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 $237.70   10.283%   $262.1427   $262.14   $262.15   $262.10  
  Purchase #2 $19.98   11.320%   $22.2417   $22.24   $22.25   $22.20  
  Purchase #3 $103.52   12.418%   $116.3751   $116.38   $116.40   $116.40  
  Purchase #4 $224.57   5.260%   $236.3824   $236.38   $236.40   $236.40  
  Purchase #5 $188.57   5.641%   $199.2072   $199.21   $199.20   $199.20  
  Purchase #6 $49.73   3.200%   $51.3214   $51.32   $51.30   $51.30  
  Purchase #7 $6.85   11.123%   $7.6119   $7.61   $7.60   $7.60  
  7 purchase totals = $830.92       $895.2824   $895.28   $895.30   $895.20