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 $80.43   9.364%   $87.9615   $87.96   $87.95   $88.00  
  Purchase #2 $231.97   4.399%   $242.1744   $242.17   $242.15   $242.20  
  Purchase #3 $97.92   4.345%   $102.1746   $102.17   $102.15   $102.20  
  Purchase #4 $113.98   7.439%   $122.459   $122.46   $122.45   $122.50  
  Purchase #5 $24.95   5.844%   $26.4081   $26.41   $26.40   $26.40  
  Purchase #6 $152.95   13.621%   $173.7833   $173.78   $173.80   $173.80  
  Purchase #7 $182.86   3.770%   $189.7538   $189.75   $189.75   $189.80  
  7 purchase totals = $885.06       $944.7147   $944.70   $944.65   $944.90