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 $238.34   9.398%   $260.7392   $260.74   $260.75   $260.70  
  Purchase #2 $240.78   7.230%   $258.1884   $258.19   $258.20   $258.20  
  Purchase #3 $241.62   4.455%   $252.3842   $252.38   $252.40   $252.40  
  Purchase #4 $167.83   3.310%   $173.3852   $173.39   $173.40   $173.40  
  Purchase #5 $198.98   4.857%   $208.6445   $208.64   $208.65   $208.60  
  Purchase #6 $59.59   13.212%   $67.463   $67.46   $67.45   $67.50  
  Purchase #7 $216.67   11.443%   $241.4635   $241.46   $241.45   $241.50  
  7 purchase totals = $1,363.81       $1,462.2680   $1,462.26   $1,462.30   $1,462.30