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 $57.95   8.585%   $62.925   $62.93   $62.95   $62.90  
  Purchase #2 $214.48   8.759%   $233.2663   $233.27   $233.25   $233.30  
  Purchase #3 $37.70   5.399%   $39.7354   $39.74   $39.75   $39.70  
  Purchase #4 $173.83   5.211%   $182.8883   $182.89   $182.90   $182.90  
  Purchase #5 $190.26   6.267%   $202.1836   $202.18   $202.20   $202.20  
  Purchase #6 $65.55   10.498%   $72.4314   $72.43   $72.45   $72.40  
  Purchase #7 $77.41   9.360%   $84.6556   $84.66   $84.65   $84.70  
  7 purchase totals = $817.18       $878.0856   $878.10   $878.15   $878.10