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 $215.99   9.614%   $236.7553   $236.76   $236.75   $236.80  
  Purchase #2 $67.39   11.630%   $75.2275   $75.23   $75.25   $75.20  
  Purchase #3 $101.30   11.323%   $112.7702   $112.77   $112.75   $112.80  
  Purchase #4 $115.47   4.219%   $120.3417   $120.34   $120.35   $120.30  
  Purchase #5 $108.57   11.119%   $120.6419   $120.64   $120.65   $120.60  
  Purchase #6 $150.34   8.808%   $163.5819   $163.58   $163.60   $163.60  
  Purchase #7 $116.95   11.774%   $130.7197   $130.72   $130.70   $130.70  
  7 purchase totals = $876.01       $960.0382   $960.04   $960.05   $960.00