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 $58.60   7.453%   $62.9675   $62.97   $62.95   $63.00  
  Purchase #2 $193.47   4.398%   $201.9788   $201.98   $202.00   $202.00  
  Purchase #3 $25.29   12.362%   $28.4163   $28.42   $28.40   $28.40  
  Purchase #4 $39.62   3.480%   $40.9988   $41.00   $41.00   $41.00  
  Purchase #5 $35.68   3.773%   $37.0262   $37.03   $37.05   $37.00  
  Purchase #6 $240.46   6.165%   $255.2844   $255.28   $255.30   $255.30  
  Purchase #7 $131.31   10.840%   $145.544   $145.54   $145.55   $145.50  
  7 purchase totals = $724.43       $772.2160   $772.22   $772.25   $772.20