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 $176.39   13.275%   $199.8058   $199.81   $199.80   $199.80  
  Purchase #2 $170.60   3.730%   $176.9634   $176.96   $176.95   $177.00  
  Purchase #3 $84.53   13.860%   $96.2459   $96.25   $96.25   $96.20  
  Purchase #4 $208.88   10.545%   $230.9064   $230.91   $230.90   $230.90  
  Purchase #5 $146.78   10.823%   $162.666   $162.67   $162.65   $162.70  
  Purchase #6 $112.55   3.292%   $116.2551   $116.26   $116.25   $116.30  
  Purchase #7 $75.43   6.583%   $80.3956   $80.40   $80.40   $80.40  
  7 purchase totals = $975.16       $1,063.2382   $1,063.26   $1,063.20   $1,063.30