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 $58.83   9.599%   $64.4771   $64.48   $64.50   $64.50  
  Purchase #2 $212.72   9.667%   $233.2836   $233.28   $233.30   $233.30  
  Purchase #3 $82.96   4.729%   $86.8832   $86.88   $86.90   $86.90  
  Purchase #4 $237.33   6.446%   $252.6283   $252.63   $252.65   $252.60  
  Purchase #5 $210.66   8.765%   $229.1243   $229.12   $229.10   $229.10  
  Purchase #6 $205.28   10.572%   $226.9822   $226.98   $227.00   $227.00  
  Purchase #7 $114.74   5.683%   $121.2607   $121.26   $121.25   $121.30  
  7 purchase totals = $1,122.52       $1,214.6394   $1,214.63   $1,214.70   $1,214.70