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 $206.43   7.465%   $221.84   $221.84   $221.85   $221.80  
  Purchase #2 $77.67   11.541%   $86.6339   $86.63   $86.65   $86.60  
  Purchase #3 $199.68   13.493%   $226.6228   $226.62   $226.60   $226.60  
  Purchase #4 $57.88   4.180%   $60.2994   $60.30   $60.30   $60.30  
  Purchase #5 $86.78   4.207%   $90.4308   $90.43   $90.45   $90.40  
  Purchase #6 $201.26   6.330%   $213.9998   $214.00   $214.00   $214.00  
  Purchase #7 $206.69   3.528%   $213.982   $213.98   $214.00   $214.00  
  7 purchase totals = $1,036.39       $1,113.8087   $1,113.80   $1,113.85   $1,113.70