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 $72.42   5.422%   $76.3466   $76.35   $76.35   $76.30  
  Purchase #2 $187.47   3.795%   $194.5845   $194.58   $194.60   $194.60  
  Purchase #3 $62.71   9.740%   $68.818   $68.82   $68.80   $68.80  
  Purchase #4 $118.52   13.869%   $134.9575   $134.96   $134.95   $135.00  
  Purchase #5 $55.41   9.575%   $60.7155   $60.72   $60.70   $60.70  
  Purchase #6 $148.28   6.295%   $157.6142   $157.61   $157.60   $157.60  
  Purchase #7 $84.77   8.759%   $92.195   $92.20   $92.20   $92.20  
  7 purchase totals = $729.58       $785.2313   $785.24   $785.20   $785.20