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 $162.76   8.506%   $176.6044   $176.60   $176.60   $176.60  
  Purchase #2 $45.35   13.769%   $51.5942   $51.59   $51.60   $51.60  
  Purchase #3 $41.48   3.725%   $43.0251   $43.03   $43.05   $43.00  
  Purchase #4 $207.29   11.496%   $231.1201   $231.12   $231.10   $231.10  
  Purchase #5 $149.30   8.428%   $161.883   $161.88   $161.90   $161.90  
  Purchase #6 $72.56   6.220%   $77.0732   $77.07   $77.05   $77.10  
  Purchase #7 $248.80   8.265%   $269.3633   $269.36   $269.35   $269.40  
  7 purchase totals = $927.54       $1,010.6633   $1,010.65   $1,010.65   $1,010.70