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 $225.42   7.647%   $242.6579   $242.66   $242.65   $242.70  
  Purchase #2 $236.84   5.816%   $250.6146   $250.61   $250.60   $250.60  
  Purchase #3 $53.64   10.165%   $59.0925   $59.09   $59.10   $59.10  
  Purchase #4 $98.27   3.203%   $101.4176   $101.42   $101.40   $101.40  
  Purchase #5 $71.48   7.136%   $76.5808   $76.58   $76.60   $76.60  
  Purchase #6 $168.73   8.264%   $182.6738   $182.67   $182.65   $182.70  
  Purchase #7 $170.80   7.102%   $182.9302   $182.93   $182.95   $182.90  
  7 purchase totals = $1,025.18       $1,095.9674   $1,095.96   $1,095.95   $1,096.00