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 $118.99   5.410%   $125.4274   $125.43   $125.45   $125.40  
  Purchase #2 $167.50   6.664%   $178.6622   $178.66   $178.65   $178.70  
  Purchase #3 $164.28   3.574%   $170.1514   $170.15   $170.15   $170.20  
  Purchase #4 $109.52   5.563%   $115.6126   $115.61   $115.60   $115.60  
  Purchase #5 $194.38   8.797%   $211.4796   $211.48   $211.50   $211.50  
  Purchase #6 $53.70   8.586%   $58.3107   $58.31   $58.30   $58.30  
  Purchase #7 $57.80   8.495%   $62.7101   $62.71   $62.70   $62.70  
  7 purchase totals = $866.17       $922.3540   $922.35   $922.35   $922.40