Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $183.93   5.302%   $193.682   $193.68   $193.70   $193.70  
  Purchase #2 $243.54   4.481%   $254.453   $254.45   $254.45   $254.50  
  Purchase #3 $213.36   13.869%   $242.9509   $242.95   $242.95   $243.00  
  Purchase #4 $152.78   6.429%   $162.6022   $162.60   $162.60   $162.60  
  Purchase #5 $221.59   4.408%   $231.3577   $231.36   $231.35   $231.40  
  Purchase #6 $182.41   13.364%   $206.7873   $206.79   $206.80   $206.80  
  Purchase #7 $224.70   13.766%   $255.6322   $255.63   $255.65   $255.60  
  7 purchase totals = $1,422.31       $1,547.4653   $1,547.46   $1,547.50   $1,547.60