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 $66.97   10.462%   $73.9764   $73.98   $74.00   $74.00  
  Purchase #2 $177.45   13.191%   $200.8574   $200.86   $200.85   $200.90  
  Purchase #3 $9.68   10.667%   $10.7126   $10.71   $10.70   $10.70  
  Purchase #4 $93.36   4.776%   $97.8189   $97.82   $97.80   $97.80  
  Purchase #5 $247.73   3.478%   $256.346   $256.35   $256.35   $256.30  
  Purchase #6 $122.76   5.848%   $129.939   $129.94   $129.95   $129.90  
  Purchase #7 $90.99   12.723%   $102.5667   $102.57   $102.55   $102.60  
  7 purchase totals = $808.94       $872.2170   $872.23   $872.20   $872.20