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 $59.72   4.470%   $62.3895   $62.39   $62.40   $62.40  
  Purchase #2 $99.85   13.123%   $112.9533   $112.95   $112.95   $113.00  
  Purchase #3 $207.75   6.558%   $221.3742   $221.37   $221.35   $221.40  
  Purchase #4 $31.67   9.340%   $34.628   $34.63   $34.65   $34.60  
  Purchase #5 $89.56   13.500%   $101.6506   $101.65   $101.65   $101.70  
  Purchase #6 $187.39   6.448%   $199.4729   $199.47   $199.45   $199.50  
  Purchase #7 $20.85   11.164%   $23.1777   $23.18   $23.20   $23.20  
  7 purchase totals = $696.79       $755.6462   $755.64   $755.65   $755.80