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 $208.42   8.200%   $225.5104   $225.51   $225.50   $225.50  
  Purchase #2 $44.40   8.564%   $48.2024   $48.20   $48.20   $48.20  
  Purchase #3 $87.27   8.274%   $94.4907   $94.49   $94.50   $94.50  
  Purchase #4 $178.44   7.591%   $191.9854   $191.99   $192.00   $192.00  
  Purchase #5 $177.56   3.257%   $183.3431   $183.34   $183.35   $183.30  
  Purchase #6 $235.66   11.275%   $262.2307   $262.23   $262.25   $262.20  
  Purchase #7 $9.95   13.255%   $11.2689   $11.27   $11.25   $11.30  
  7 purchase totals = $941.70       $1,017.0316   $1,017.03   $1,017.05   $1,017.00