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 $197.61   6.527%   $210.508   $210.51   $210.50   $210.50  
  Purchase #2 $125.89   6.278%   $133.7934   $133.79   $133.80   $133.80  
  Purchase #3 $61.34   13.457%   $69.5945   $69.59   $69.60   $69.60  
  Purchase #4 $141.58   12.203%   $158.857   $158.86   $158.85   $158.90  
  Purchase #5 $182.65   11.321%   $203.3278   $203.33   $203.35   $203.30  
  Purchase #6 $155.73   9.459%   $170.4605   $170.46   $170.45   $170.50  
  Purchase #7 $185.70   7.213%   $199.0945   $199.09   $199.10   $199.10  
  7 purchase totals = $1,050.50       $1,145.6357   $1,145.63   $1,145.65   $1,145.70