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 $108.46   5.293%   $114.2008   $114.20   $114.20   $114.20  
  Purchase #2 $146.87   8.465%   $159.3025   $159.30   $159.30   $159.30  
  Purchase #3 $28.94   12.120%   $32.4475   $32.45   $32.45   $32.40  
  Purchase #4 $189.63   5.869%   $200.7594   $200.76   $200.75   $200.80  
  Purchase #5 $155.54   4.224%   $162.11   $162.11   $162.10   $162.10  
  Purchase #6 $139.56   9.528%   $152.8573   $152.86   $152.85   $152.90  
  Purchase #7 $202.48   6.472%   $215.5845   $215.58   $215.60   $215.60  
  7 purchase totals = $971.48       $1,037.2620   $1,037.26   $1,037.25   $1,037.30