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 $116.47   8.178%   $125.9949   $125.99   $126.00   $126.00  
  Purchase #2 $161.42   10.372%   $178.1625   $178.16   $178.15   $178.20  
  Purchase #3 $25.68   8.579%   $27.8831   $27.88   $27.90   $27.90  
  Purchase #4 $245.70   11.488%   $273.926   $273.93   $273.95   $273.90  
  Purchase #5 $225.59   4.870%   $236.5762   $236.58   $236.60   $236.60  
  Purchase #6 $181.68   5.399%   $191.4889   $191.49   $191.50   $191.50  
  Purchase #7 $130.61   8.341%   $141.5042   $141.50   $141.50   $141.50  
  7 purchase totals = $1,087.15       $1,175.5358   $1,175.53   $1,175.60   $1,175.60