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 $85.62   12.205%   $96.0699   $96.07   $96.05   $96.10  
  Purchase #2 $246.40   13.515%   $279.701   $279.70   $279.70   $279.70  
  Purchase #3 $55.32   10.129%   $60.9234   $60.92   $60.90   $60.90  
  Purchase #4 $60.27   7.143%   $64.5751   $64.58   $64.60   $64.60  
  Purchase #5 $72.39   5.355%   $76.2665   $76.27   $76.25   $76.30  
  Purchase #6 $183.39   6.217%   $194.7914   $194.79   $194.80   $194.80  
  Purchase #7 $167.40   11.535%   $186.7096   $186.71   $186.70   $186.70  
  7 purchase totals = $870.79       $959.0369   $959.04   $959.00   $959.10