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 $86.82   10.526%   $95.9587   $95.96   $95.95   $96.00  
  Purchase #2 $170.72   12.717%   $192.4305   $192.43   $192.45   $192.40  
  Purchase #3 $24.53   7.463%   $26.3607   $26.36   $26.35   $26.40  
  Purchase #4 $149.26   9.211%   $163.0083   $163.01   $163.00   $163.00  
  Purchase #5 $217.28   3.472%   $224.824   $224.82   $224.80   $224.80  
  Purchase #6 $176.80   5.553%   $186.6177   $186.62   $186.60   $186.60  
  Purchase #7 $104.54   8.426%   $113.3485   $113.35   $113.35   $113.30  
  7 purchase totals = $929.95       $1,002.5484   $1,002.55   $1,002.50   $1,002.50