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 $121.63   3.575%   $125.9783   $125.98   $126.00   $126.00  
  Purchase #2 $62.96   4.652%   $65.8889   $65.89   $65.90   $65.90  
  Purchase #3 $22.88   13.663%   $26.0061   $26.01   $26.00   $26.00  
  Purchase #4 $211.88   11.517%   $236.2822   $236.28   $236.30   $236.30  
  Purchase #5 $205.46   4.693%   $215.1022   $215.10   $215.10   $215.10  
  Purchase #6 $139.32   11.271%   $155.0228   $155.02   $155.00   $155.00  
  Purchase #7 $211.60   8.266%   $229.0909   $229.09   $229.10   $229.10  
  7 purchase totals = $975.73       $1,053.3714   $1,053.37   $1,053.40   $1,053.40