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 $241.85   4.620%   $253.0235   $253.02   $253.00   $253.00  
  Purchase #2 $232.40   5.794%   $245.8653   $245.87   $245.85   $245.90  
  Purchase #3 $240.63   11.784%   $268.9858   $268.99   $269.00   $269.00  
  Purchase #4 $232.45   6.201%   $246.8642   $246.86   $246.85   $246.90  
  Purchase #5 $44.82   4.465%   $46.8212   $46.82   $46.80   $46.80  
  Purchase #6 $72.41   11.541%   $80.7668   $80.77   $80.75   $80.80  
  Purchase #7 $239.80   7.603%   $258.032   $258.03   $258.05   $258.00  
  7 purchase totals = $1,304.36       $1,400.3588   $1,400.36   $1,400.30   $1,400.40