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 $68.42   10.513%   $75.613   $75.61   $75.60   $75.60  
  Purchase #2 $167.59   9.318%   $183.206   $183.21   $183.20   $183.20  
  Purchase #3 $34.36   9.529%   $37.6342   $37.63   $37.65   $37.60  
  Purchase #4 $47.98   4.697%   $50.2336   $50.23   $50.25   $50.20  
  Purchase #5 $244.74   6.382%   $260.3593   $260.36   $260.35   $260.40  
  Purchase #6 $125.96   9.365%   $137.7562   $137.76   $137.75   $137.80  
  Purchase #7 $188.99   5.662%   $199.6906   $199.69   $199.70   $199.70  
  7 purchase totals = $878.04       $944.4929   $944.49   $944.50   $944.50