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 $183.53   7.516%   $197.3241   $197.32   $197.30   $197.30  
  Purchase #2 $217.73   10.482%   $240.5525   $240.55   $240.55   $240.60  
  Purchase #3 $63.87   4.544%   $66.7723   $66.77   $66.75   $66.80  
  Purchase #4 $206.92   5.326%   $217.9406   $217.94   $217.95   $217.90  
  Purchase #5 $65.74   11.722%   $73.446   $73.45   $73.45   $73.40  
  Purchase #6 $221.88   6.296%   $235.8496   $235.85   $235.85   $235.80  
  Purchase #7 $250.91   5.344%   $264.3186   $264.32   $264.30   $264.30  
  7 purchase totals = $1,210.58       $1,296.2037   $1,296.20   $1,296.15   $1,296.10