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 $118.60   6.377%   $126.1631   $126.16   $126.15   $126.20  
  Purchase #2 $198.64   7.586%   $213.7088   $213.71   $213.70   $213.70  
  Purchase #3 $61.85   10.432%   $68.3022   $68.30   $68.30   $68.30  
  Purchase #4 $59.99   3.632%   $62.1688   $62.17   $62.15   $62.20  
  Purchase #5 $189.75   3.507%   $196.4045   $196.40   $196.40   $196.40  
  Purchase #6 $240.33   9.619%   $263.4473   $263.45   $263.45   $263.40  
  Purchase #7 $27.30   11.150%   $30.344   $30.34   $30.35   $30.30  
  7 purchase totals = $896.46       $960.5387   $960.53   $960.50   $960.50