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 $216.86   5.211%   $228.1606   $228.16   $228.15   $228.20  
  Purchase #2 $139.99   4.756%   $146.6479   $146.65   $146.65   $146.60  
  Purchase #3 $98.36   13.458%   $111.5973   $111.60   $111.60   $111.60  
  Purchase #4 $178.25   10.120%   $196.2889   $196.29   $196.30   $196.30  
  Purchase #5 $6.25   6.371%   $6.6482   $6.65   $6.65   $6.60  
  Purchase #6 $125.27   10.394%   $138.2906   $138.29   $138.30   $138.30  
  Purchase #7 $180.30   8.612%   $195.8274   $195.83   $195.85   $195.80  
  7 purchase totals = $945.28       $1,023.4609   $1,023.47   $1,023.50   $1,023.40