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 $76.49   12.410%   $85.9824   $85.98   $86.00   $86.00  
  Purchase #2 $116.26   12.721%   $131.0494   $131.05   $131.05   $131.00  
  Purchase #3 $193.58   12.502%   $217.7814   $217.78   $217.80   $217.80  
  Purchase #4 $22.87   5.502%   $24.1283   $24.13   $24.15   $24.10  
  Purchase #5 $134.93   13.863%   $153.6353   $153.64   $153.65   $153.60  
  Purchase #6 $175.74   10.797%   $194.7146   $194.71   $194.70   $194.70  
  Purchase #7 $231.87   9.805%   $254.6049   $254.60   $254.60   $254.60  
  7 purchase totals = $951.74       $1,061.8963   $1,061.89   $1,061.95   $1,061.80