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 $213.75   4.147%   $222.6142   $222.61   $222.60   $222.60  
  Purchase #2 $233.29   6.306%   $248.0013   $248.00   $248.00   $248.00  
  Purchase #3 $241.50   13.151%   $273.2597   $273.26   $273.25   $273.30  
  Purchase #4 $129.89   4.740%   $136.0468   $136.05   $136.05   $136.00  
  Purchase #5 $160.92   6.149%   $170.815   $170.82   $170.80   $170.80  
  Purchase #6 $228.41   3.505%   $236.4158   $236.42   $236.40   $236.40  
  Purchase #7 $53.90   13.204%   $61.017   $61.02   $61.00   $61.00  
  7 purchase totals = $1,261.66       $1,348.1698   $1,348.18   $1,348.10   $1,348.10