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 $44.68   6.230%   $47.4636   $47.46   $47.45   $47.50  
  Purchase #2 $119.71   13.437%   $135.7954   $135.80   $135.80   $135.80  
  Purchase #3 $96.60   4.655%   $101.0967   $101.10   $101.10   $101.10  
  Purchase #4 $32.39   11.146%   $36.0002   $36.00   $36.00   $36.00  
  Purchase #5 $230.77   5.497%   $243.4554   $243.46   $243.45   $243.50  
  Purchase #6 $149.93   3.739%   $155.5359   $155.54   $155.55   $155.50  
  Purchase #7 $132.95   7.793%   $143.3108   $143.31   $143.30   $143.30  
  7 purchase totals = $807.03       $862.6580   $862.67   $862.65   $862.70