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 $48.90   8.467%   $53.0404   $53.04   $53.05   $53.00  
  Purchase #2 $25.88   13.206%   $29.2977   $29.30   $29.30   $29.30  
  Purchase #3 $163.32   3.212%   $168.5658   $168.57   $168.55   $168.60  
  Purchase #4 $122.27   4.472%   $127.7379   $127.74   $127.75   $127.70  
  Purchase #5 $68.57   12.287%   $76.9952   $77.00   $77.00   $77.00  
  Purchase #6 $75.61   6.406%   $80.4536   $80.45   $80.45   $80.50  
  Purchase #7 $190.92   5.242%   $200.928   $200.93   $200.95   $200.90  
  7 purchase totals = $695.47       $737.0186   $737.03   $737.05   $737.00