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 $230.88   4.767%   $241.886   $241.89   $241.90   $241.90  
  Purchase #2 $110.93   4.553%   $115.9806   $115.98   $116.00   $116.00  
  Purchase #3 $65.34   4.173%   $68.0666   $68.07   $68.05   $68.10  
  Purchase #4 $155.75   13.529%   $176.8214   $176.82   $176.80   $176.80  
  Purchase #5 $82.71   13.844%   $94.1604   $94.16   $94.15   $94.20  
  Purchase #6 $204.49   6.296%   $217.3647   $217.36   $217.35   $217.40  
  Purchase #7 $47.96   11.143%   $53.3042   $53.30   $53.30   $53.30  
  7 purchase totals = $898.06       $967.5839   $967.58   $967.55   $967.70