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 $64.96   11.299%   $72.2998   $72.30   $72.30   $72.30  
  Purchase #2 $112.67   5.428%   $118.7857   $118.79   $118.80   $118.80  
  Purchase #3 $39.61   4.874%   $41.5406   $41.54   $41.55   $41.50  
  Purchase #4 $231.92   7.177%   $248.5649   $248.56   $248.55   $248.60  
  Purchase #5 $112.87   7.259%   $121.0632   $121.06   $121.05   $121.10  
  Purchase #6 $45.59   6.632%   $48.6135   $48.61   $48.60   $48.60  
  Purchase #7 $68.76   9.197%   $75.0839   $75.08   $75.10   $75.10  
  7 purchase totals = $676.38       $725.9516   $725.94   $725.95   $726.00