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 $141.50   9.269%   $154.6156   $154.62   $154.60   $154.60  
  Purchase #2 $185.29   6.435%   $197.2134   $197.21   $197.20   $197.20  
  Purchase #3 $217.92   6.703%   $232.5272   $232.53   $232.55   $232.50  
  Purchase #4 $232.25   13.347%   $263.2484   $263.25   $263.25   $263.20  
  Purchase #5 $54.77   13.652%   $62.2472   $62.25   $62.25   $62.20  
  Purchase #6 $30.25   5.808%   $32.0069   $32.01   $32.00   $32.00  
  Purchase #7 $80.78   4.363%   $84.3044   $84.30   $84.30   $84.30  
  7 purchase totals = $942.76       $1,026.1631   $1,026.17   $1,026.15   $1,026.00