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 $86.25   10.667%   $95.4503   $95.45   $95.45   $95.50  
  Purchase #2 $185.55   8.563%   $201.4386   $201.44   $201.45   $201.40  
  Purchase #3 $20.73   11.141%   $23.0395   $23.04   $23.05   $23.00  
  Purchase #4 $60.36   8.273%   $65.3536   $65.35   $65.35   $65.40  
  Purchase #5 $197.54   5.417%   $208.2407   $208.24   $208.25   $208.20  
  Purchase #6 $47.83   7.203%   $51.2752   $51.28   $51.30   $51.30  
  Purchase #7 $95.59   11.722%   $106.7951   $106.80   $106.80   $106.80  
  7 purchase totals = $693.85       $751.5930   $751.60   $751.65   $751.60