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 $22.95   12.122%   $25.732   $25.73   $25.75   $25.70  
  Purchase #2 $165.75   3.574%   $171.6739   $171.67   $171.65   $171.70  
  Purchase #3 $118.31   12.388%   $132.9662   $132.97   $132.95   $133.00  
  Purchase #4 $213.56   3.772%   $221.6155   $221.62   $221.60   $221.60  
  Purchase #5 $163.60   11.543%   $182.4843   $182.48   $182.50   $182.50  
  Purchase #6 $54.45   10.423%   $60.1253   $60.13   $60.15   $60.10  
  Purchase #7 $230.54   6.254%   $244.958   $244.96   $244.95   $245.00  
  7 purchase totals = $969.16       $1,039.5552   $1,039.56   $1,039.55   $1,039.60