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	$242.27	8.603%	$263.1125	$263.11	$263.10	$263.10
Purchase #2	$86.71	4.118%	$90.2807	$90.28	$90.30	$90.30
Purchase #3	$214.67	5.379%	$226.2171	$226.22	$226.20	$226.20
Purchase #4	$50.29	8.400%	$54.5144	$54.51	$54.50	$54.50
Purchase #5	$122.71	4.241%	$127.9141	$127.91	$127.90	$127.90
Purchase #6	$40.70	5.753%	$43.0415	$43.04	$43.05	$43.00
Purchase #7	$54.60	10.861%	$60.5301	$60.53	$60.55	$60.50
7 purchase totals =	$811.95		$865.6104	$865.60	$865.60	$865.50