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 $111.78   12.687%   $125.9615   $125.96   $125.95   $126.00  
  Purchase #2 $52.47   10.450%   $57.9531   $57.95   $57.95   $58.00  
  Purchase #3 $120.47   10.572%   $133.2061   $133.21   $133.20   $133.20  
  Purchase #4 $185.25   12.184%   $207.8209   $207.82   $207.80   $207.80  
  Purchase #5 $199.47   9.236%   $217.893   $217.89   $217.90   $217.90  
  Purchase #6 $222.83   12.290%   $250.2158   $250.22   $250.20   $250.20  
  Purchase #7 $73.99   4.272%   $77.1509   $77.15   $77.15   $77.20  
  7 purchase totals = $966.26       $1,070.2013   $1,070.20   $1,070.15   $1,070.30