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 $61.55   11.285%   $68.4959   $68.50   $68.50   $68.50  
  Purchase #2 $83.58   13.642%   $94.982   $94.98   $95.00   $95.00  
  Purchase #3 $16.99   3.641%   $17.6086   $17.61   $17.60   $17.60  
  Purchase #4 $47.62   9.116%   $51.961   $51.96   $51.95   $52.00  
  Purchase #5 $6.48   8.530%   $7.0327   $7.03   $7.05   $7.00  
  Purchase #6 $192.74   3.295%   $199.0908   $199.09   $199.10   $199.10  
  Purchase #7 $55.92   11.754%   $62.4928   $62.49   $62.50   $62.50  
  7 purchase totals = $464.88       $501.6638   $501.66   $501.70   $501.70