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	$61.85	5.544%	$65.279	$65.28	$65.30	$65.30
Purchase #2	$176.76	13.545%	$200.7021	$200.70	$200.70	$200.70
Purchase #3	$80.94	11.698%	$90.4084	$90.41	$90.40	$90.40
Purchase #4	$149.25	11.266%	$166.0645	$166.06	$166.05	$166.10
Purchase #5	$247.69	10.575%	$273.8832	$273.88	$273.90	$273.90
Purchase #6	$172.83	4.404%	$180.4414	$180.44	$180.45	$180.40
Purchase #7	$10.91	3.433%	$11.2845	$11.28	$11.30	$11.30
7 purchase totals =	$900.23		$988.0631	$988.05	$988.10	$988.10