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	$39.34	10.851%	$43.6088	$43.61	$43.60	$43.60
Purchase #2	$215.98	4.444%	$225.5782	$225.58	$225.60	$225.60
Purchase #3	$113.54	8.356%	$123.0274	$123.03	$123.05	$123.00
Purchase #4	$57.71	5.789%	$61.0508	$61.05	$61.05	$61.10
Purchase #5	$45.78	11.738%	$51.1537	$51.15	$51.15	$51.20
Purchase #6	$242.31	12.829%	$273.3959	$273.40	$273.40	$273.40
Purchase #7	$22.93	9.872%	$25.1936	$25.19	$25.20	$25.20
7 purchase totals =	$737.59		$803.0084	$803.01	$803.05	$803.10