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 $208.76   13.831%   $237.6336   $237.63   $237.65   $237.60  
  Purchase #2 $155.69   13.677%   $176.9837   $176.98   $177.00   $177.00  
  Purchase #3 $119.80   4.819%   $125.5732   $125.57   $125.55   $125.60  
  Purchase #4 $106.60   3.411%   $110.2361   $110.24   $110.25   $110.20  
  Purchase #5 $135.93   5.275%   $143.1003   $143.10   $143.10   $143.10  
  Purchase #6 $63.66   9.274%   $69.5638   $69.56   $69.55   $69.60  
  Purchase #7 $146.69   8.322%   $158.8975   $158.90   $158.90   $158.90  
  7 purchase totals = $937.13       $1,021.9882   $1,021.98   $1,022.00   $1,022.00