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 $118.82   5.475%   $125.3254   $125.33   $125.35   $125.30  
  Purchase #2 $109.97   6.609%   $117.2379   $117.24   $117.25   $117.20  
  Purchase #3 $95.55   10.218%   $105.3133   $105.31   $105.30   $105.30  
  Purchase #4 $133.59   5.596%   $141.0657   $141.07   $141.05   $141.10  
  Purchase #5 $8.55   3.661%   $8.863   $8.86   $8.85   $8.90  
  Purchase #6 $217.96   13.133%   $246.5847   $246.58   $246.60   $246.60  
  Purchase #7 $23.59   8.522%   $25.6003   $25.60   $25.60   $25.60  
  7 purchase totals = $708.03       $769.9903   $769.99   $770.00   $770.00