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 $85.35   11.344%   $95.0321   $95.03   $95.05   $95.00  
  Purchase #2 $49.64   10.836%   $55.019   $55.02   $55.00   $55.00  
  Purchase #3 $124.38   11.541%   $138.7347   $138.73   $138.75   $138.70  
  Purchase #4 $60.51   5.591%   $63.8931   $63.89   $63.90   $63.90  
  Purchase #5 $72.69   9.267%   $79.4262   $79.43   $79.45   $79.40  
  Purchase #6 $249.49   9.535%   $273.2789   $273.28   $273.30   $273.30  
  Purchase #7 $69.37   5.784%   $73.3824   $73.38   $73.40   $73.40  
  7 purchase totals = $711.43       $778.7664   $778.76   $778.85   $778.70