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 $41.76   10.814%   $46.2759   $46.28   $46.30   $46.30  
  Purchase #2 $210.29   8.558%   $228.2866   $228.29   $228.30   $228.30  
  Purchase #3 $70.78   4.695%   $74.1031   $74.10   $74.10   $74.10  
  Purchase #4 $168.89   6.755%   $180.2985   $180.30   $180.30   $180.30  
  Purchase #5 $154.54   8.470%   $167.6295   $167.63   $167.65   $167.60  
  Purchase #6 $38.49   13.866%   $43.827   $43.83   $43.85   $43.80  
  Purchase #7 $25.38   9.266%   $27.7317   $27.73   $27.75   $27.70  
  7 purchase totals = $710.13       $768.1523   $768.16   $768.25   $768.10