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 $208.63   7.764%   $224.828   $224.83   $224.85   $224.80  
  Purchase #2 $113.35   10.362%   $125.0953   $125.10   $125.10   $125.10  
  Purchase #3 $39.99   8.337%   $43.324   $43.32   $43.30   $43.30  
  Purchase #4 $247.79   8.732%   $269.427   $269.43   $269.45   $269.40  
  Purchase #5 $216.83   8.123%   $234.4431   $234.44   $234.45   $234.40  
  Purchase #6 $225.67   3.872%   $234.4079   $234.41   $234.40   $234.40  
  Purchase #7 $205.90   13.639%   $233.9827   $233.98   $234.00   $234.00  
  7 purchase totals = $1,258.16       $1,365.5080   $1,365.51   $1,365.55   $1,365.40