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 $195.46   7.590%   $210.2954   $210.30   $210.30   $210.30  
  Purchase #2 $151.54   5.219%   $159.4489   $159.45   $159.45   $159.40  
  Purchase #3 $67.68   13.256%   $76.6517   $76.65   $76.65   $76.70  
  Purchase #4 $194.49   6.186%   $206.5212   $206.52   $206.50   $206.50  
  Purchase #5 $80.75   3.174%   $83.313   $83.31   $83.30   $83.30  
  Purchase #6 $14.69   7.555%   $15.7998   $15.80   $15.80   $15.80  
  Purchase #7 $223.48   3.420%   $231.123   $231.12   $231.10   $231.10  
  7 purchase totals = $928.09       $983.1530   $983.15   $983.10   $983.10