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 $72.46   8.787%   $78.8271   $78.83   $78.85   $78.80  
  Purchase #2 $216.66   8.430%   $234.9244   $234.92   $234.90   $234.90  
  Purchase #3 $152.27   13.593%   $172.9681   $172.97   $172.95   $173.00  
  Purchase #4 $126.44   6.838%   $135.086   $135.09   $135.10   $135.10  
  Purchase #5 $73.39   3.601%   $76.0328   $76.03   $76.05   $76.00  
  Purchase #6 $210.27   8.634%   $228.4247   $228.42   $228.40   $228.40  
  Purchase #7 $213.94   5.817%   $226.3849   $226.38   $226.40   $226.40  
  7 purchase totals = $1,065.43       $1,152.6480   $1,152.64   $1,152.65   $1,152.60