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 $94.93   3.196%   $97.964   $97.96   $97.95   $98.00  
  Purchase #2 $226.70   6.809%   $242.136   $242.14   $242.15   $242.10  
  Purchase #3 $199.54   9.133%   $217.764   $217.76   $217.75   $217.80  
  Purchase #4 $153.93   4.258%   $160.4843   $160.48   $160.50   $160.50  
  Purchase #5 $168.69   8.323%   $182.7301   $182.73   $182.75   $182.70  
  Purchase #6 $140.96   12.175%   $158.1219   $158.12   $158.10   $158.10  
  Purchase #7 $198.86   5.296%   $209.3916   $209.39   $209.40   $209.40  
  7 purchase totals = $1,183.61       $1,268.5919   $1,268.58   $1,268.60   $1,268.60