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 $175.33   11.553%   $195.5859   $195.59   $195.60   $195.60  
  Purchase #2 $136.30   7.444%   $146.4462   $146.45   $146.45   $146.40  
  Purchase #3 $106.42   12.467%   $119.6874   $119.69   $119.70   $119.70  
  Purchase #4 $152.67   6.756%   $162.9844   $162.98   $163.00   $163.00  
  Purchase #5 $49.60   6.144%   $52.6474   $52.65   $52.65   $52.60  
  Purchase #6 $113.63   11.416%   $126.602   $126.60   $126.60   $126.60  
  Purchase #7 $144.92   9.439%   $158.599   $158.60   $158.60   $158.60  
  7 purchase totals = $878.87       $962.5523   $962.56   $962.60   $962.50