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 $68.96   11.761%   $77.0704   $77.07   $77.05   $77.10  
  Purchase #2 $91.88   4.733%   $96.2287   $96.23   $96.25   $96.20  
  Purchase #3 $203.94   6.419%   $217.0309   $217.03   $217.05   $217.00  
  Purchase #4 $153.63   8.341%   $166.4443   $166.44   $166.45   $166.40  
  Purchase #5 $159.61   11.513%   $177.9859   $177.99   $178.00   $178.00  
  Purchase #6 $142.48   9.203%   $155.5924   $155.59   $155.60   $155.60  
  Purchase #7 $231.66   13.181%   $262.1951   $262.20   $262.20   $262.20  
  7 purchase totals = $1,052.16       $1,152.5477   $1,152.55   $1,152.60   $1,152.50