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 $152.29   7.234%   $163.3067   $163.31   $163.30   $163.30  
  Purchase #2 $56.94   9.449%   $62.3203   $62.32   $62.30   $62.30  
  Purchase #3 $43.92   9.717%   $48.1877   $48.19   $48.20   $48.20  
  Purchase #4 $155.83   12.599%   $175.463   $175.46   $175.45   $175.50  
  Purchase #5 $206.78   13.557%   $234.8132   $234.81   $234.80   $234.80  
  Purchase #6 $244.54   8.846%   $266.172   $266.17   $266.15   $266.20  
  Purchase #7 $97.97   3.854%   $101.7458   $101.75   $101.75   $101.70  
  7 purchase totals = $958.27       $1,052.0087   $1,052.01   $1,051.95   $1,052.00