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 $96.57   5.568%   $101.947   $101.95   $101.95   $101.90  
  Purchase #2 $203.90   11.696%   $227.7481   $227.75   $227.75   $227.70  
  Purchase #3 $210.91   7.556%   $226.8464   $226.85   $226.85   $226.80  
  Purchase #4 $154.71   8.782%   $168.2966   $168.30   $168.30   $168.30  
  Purchase #5 $94.89   13.331%   $107.5398   $107.54   $107.55   $107.50  
  Purchase #6 $188.48   3.385%   $194.86   $194.86   $194.85   $194.90  
  Purchase #7 $17.69   8.180%   $19.137   $19.14   $19.15   $19.10  
  7 purchase totals = $967.15       $1,046.3749   $1,046.39   $1,046.40   $1,046.20