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 $46.34   5.798%   $49.0268   $49.03   $49.05   $49.00  
  Purchase #2 $225.97   5.252%   $237.8379   $237.84   $237.85   $237.80  
  Purchase #3 $89.29   8.798%   $97.1457   $97.15   $97.15   $97.10  
  Purchase #4 $246.36   4.118%   $256.5051   $256.51   $256.50   $256.50  
  Purchase #5 $170.82   11.597%   $190.63   $190.63   $190.65   $190.60  
  Purchase #6 $161.67   7.233%   $173.3636   $173.36   $173.35   $173.40  
  Purchase #7 $34.40   8.218%   $37.227   $37.23   $37.25   $37.20  
  7 purchase totals = $974.85       $1,041.7361   $1,041.75   $1,041.80   $1,041.60