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 $142.76   5.590%   $150.7403   $150.74   $150.75   $150.70  
  Purchase #2 $64.94   4.137%   $67.6266   $67.63   $67.65   $67.60  
  Purchase #3 $60.56   8.177%   $65.512   $65.51   $65.50   $65.50  
  Purchase #4 $180.92   8.162%   $195.6867   $195.69   $195.70   $195.70  
  Purchase #5 $221.92   6.755%   $236.9107   $236.91   $236.90   $236.90  
  Purchase #6 $244.82   3.588%   $253.6041   $253.60   $253.60   $253.60  
  Purchase #7 $193.53   9.846%   $212.585   $212.59   $212.60   $212.60  
  7 purchase totals = $1,109.45       $1,182.6654   $1,182.67   $1,182.70   $1,182.60