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 $41.50   11.670%   $46.3431   $46.34   $46.35   $46.30  
  Purchase #2 $201.62   4.810%   $211.3179   $211.32   $211.30   $211.30  
  Purchase #3 $115.37   8.258%   $124.8973   $124.90   $124.90   $124.90  
  Purchase #4 $19.90   7.838%   $21.4598   $21.46   $21.45   $21.50  
  Purchase #5 $224.87   5.339%   $236.8758   $236.88   $236.90   $236.90  
  Purchase #6 $86.77   6.727%   $92.607   $92.61   $92.60   $92.60  
  Purchase #7 $130.78   10.267%   $144.2072   $144.21   $144.20   $144.20  
  7 purchase totals = $820.81       $877.7081   $877.72   $877.70   $877.70