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 $62.43   8.842%   $67.9501   $67.95   $67.95   $68.00  
  Purchase #2 $213.64   12.678%   $240.7253   $240.73   $240.75   $240.70  
  Purchase #3 $186.27   4.391%   $194.4491   $194.45   $194.45   $194.40  
  Purchase #4 $52.61   3.395%   $54.3961   $54.40   $54.40   $54.40  
  Purchase #5 $119.74   5.852%   $126.7472   $126.75   $126.75   $126.70  
  Purchase #6 $26.45   13.355%   $29.9824   $29.98   $30.00   $30.00  
  Purchase #7 $22.90   10.864%   $25.3879   $25.39   $25.40   $25.40  
  7 purchase totals = $684.04       $739.6381   $739.65   $739.70   $739.60