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 $214.97   7.113%   $230.2608   $230.26   $230.25   $230.30  
  Purchase #2 $43.69   9.243%   $47.7283   $47.73   $47.75   $47.70  
  Purchase #3 $184.47   8.277%   $199.7386   $199.74   $199.75   $199.70  
  Purchase #4 $163.35   11.547%   $182.212   $182.21   $182.20   $182.20  
  Purchase #5 $167.82   8.844%   $182.662   $182.66   $182.65   $182.70  
  Purchase #6 $232.57   11.191%   $258.5969   $258.60   $258.60   $258.60  
  Purchase #7 $185.36   10.549%   $204.9136   $204.91   $204.90   $204.90  
  7 purchase totals = $1,192.23       $1,306.1122   $1,306.11   $1,306.10   $1,306.10