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 $119.49   5.746%   $126.3559   $126.36   $126.35   $126.40  
  Purchase #2 $230.43   6.477%   $245.355   $245.36   $245.35   $245.40  
  Purchase #3 $191.48   13.373%   $217.0866   $217.09   $217.10   $217.10  
  Purchase #4 $104.42   13.340%   $118.3496   $118.35   $118.35   $118.30  
  Purchase #5 $222.72   3.323%   $230.121   $230.12   $230.10   $230.10  
  Purchase #6 $38.34   11.325%   $42.682   $42.68   $42.70   $42.70  
  Purchase #7 $192.35   12.230%   $215.8744   $215.87   $215.85   $215.90  
  7 purchase totals = $1,099.23       $1,195.8245   $1,195.83   $1,195.80   $1,195.90