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 $68.70   7.636%   $73.9459   $73.95   $73.95   $73.90  
  Purchase #2 $150.66   10.510%   $166.4944   $166.49   $166.50   $166.50  
  Purchase #3 $168.38   8.298%   $182.3522   $182.35   $182.35   $182.40  
  Purchase #4 $138.77   9.664%   $152.1807   $152.18   $152.20   $152.20  
  Purchase #5 $62.41   8.773%   $67.8852   $67.89   $67.90   $67.90  
  Purchase #6 $81.95   6.177%   $87.0121   $87.01   $87.00   $87.00  
  Purchase #7 $191.37   8.517%   $207.669   $207.67   $207.65   $207.70  
  7 purchase totals = $862.24       $937.5395   $937.54   $937.55   $937.60