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 $86.56   11.601%   $96.6018   $96.60   $96.60   $96.60  
  Purchase #2 $158.47   5.574%   $167.3031   $167.30   $167.30   $167.30  
  Purchase #3 $108.39   6.755%   $115.7117   $115.71   $115.70   $115.70  
  Purchase #4 $98.39   5.641%   $103.9402   $103.94   $103.95   $103.90  
  Purchase #5 $70.45   10.833%   $78.0818   $78.08   $78.10   $78.10  
  Purchase #6 $231.86   12.548%   $260.9538   $260.95   $260.95   $261.00  
  Purchase #7 $47.54   8.386%   $51.5267   $51.53   $51.55   $51.50  
  7 purchase totals = $801.66       $874.1191   $874.11   $874.15   $874.10