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 $37.46   10.149%   $41.2618   $41.26   $41.25   $41.30  
  Purchase #2 $245.37   12.739%   $276.6277   $276.63   $276.65   $276.60  
  Purchase #3 $123.41   9.374%   $134.9785   $134.98   $135.00   $135.00  
  Purchase #4 $51.41   7.827%   $55.4339   $55.43   $55.45   $55.40  
  Purchase #5 $238.51   5.276%   $251.0938   $251.09   $251.10   $251.10  
  Purchase #6 $121.87   6.432%   $129.7087   $129.71   $129.70   $129.70  
  Purchase #7 $186.64   3.463%   $193.1033   $193.10   $193.10   $193.10  
  7 purchase totals = $1,004.67       $1,082.2077   $1,082.20   $1,082.25   $1,082.20