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 $245.83   8.769%   $267.3868   $267.39   $267.40   $267.40  
  Purchase #2 $207.97   4.150%   $216.6008   $216.60   $216.60   $216.60  
  Purchase #3 $105.47   13.655%   $119.8719   $119.87   $119.85   $119.90  
  Purchase #4 $77.82   10.494%   $85.9864   $85.99   $86.00   $86.00  
  Purchase #5 $98.44   6.283%   $104.625   $104.63   $104.65   $104.60  
  Purchase #6 $121.53   4.118%   $126.5346   $126.53   $126.55   $126.50  
  Purchase #7 $12.82   9.197%   $13.9991   $14.00   $14.00   $14.00  
  7 purchase totals = $869.88       $935.0046   $935.01   $935.05   $935.00