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 $92.33   3.138%   $95.2273   $95.23   $95.25   $95.20  
  Purchase #2 $225.69   4.349%   $235.5053   $235.51   $235.50   $235.50  
  Purchase #3 $65.70   5.696%   $69.4423   $69.44   $69.45   $69.40  
  Purchase #4 $98.52   6.713%   $105.1336   $105.13   $105.15   $105.10  
  Purchase #5 $40.95   11.219%   $45.5442   $45.54   $45.55   $45.50  
  Purchase #6 $42.46   8.573%   $46.1001   $46.10   $46.10   $46.10  
  Purchase #7 $203.36   3.370%   $210.2132   $210.21   $210.20   $210.20  
  7 purchase totals = $769.01       $807.1660   $807.16   $807.20   $807.00