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 $228.26   7.567%   $245.5324   $245.53   $245.55   $245.50  
  Purchase #2 $104.35   10.616%   $115.4278   $115.43   $115.45   $115.40  
  Purchase #3 $241.88   3.873%   $251.248   $251.25   $251.25   $251.20  
  Purchase #4 $72.59   4.233%   $75.6627   $75.66   $75.65   $75.70  
  Purchase #5 $184.73   12.565%   $207.9413   $207.94   $207.95   $207.90  
  Purchase #6 $44.62   4.848%   $46.7832   $46.78   $46.80   $46.80  
  Purchase #7 $140.53   8.120%   $151.941   $151.94   $151.95   $151.90  
  7 purchase totals = $1,016.96       $1,094.5364   $1,094.53   $1,094.60   $1,094.40