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 $163.95   7.499%   $176.2446   $176.24   $176.25   $176.20  
  Purchase #2 $232.41   5.484%   $245.1554   $245.16   $245.15   $245.20  
  Purchase #3 $215.34   3.390%   $222.64   $222.64   $222.65   $222.60  
  Purchase #4 $61.48   5.731%   $65.0034   $65.00   $65.00   $65.00  
  Purchase #5 $59.79   9.600%   $65.5298   $65.53   $65.55   $65.50  
  Purchase #6 $101.63   10.675%   $112.479   $112.48   $112.50   $112.50  
  Purchase #7 $42.75   6.776%   $45.6467   $45.65   $45.65   $45.60  
  7 purchase totals = $877.35       $932.6989   $932.70   $932.75   $932.60