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	$115.40	10.715%	$127.7651	$127.77	$127.75	$127.80
Purchase #2	$184.69	8.632%	$200.6324	$200.63	$200.65	$200.60
Purchase #3	$109.29	8.496%	$118.5753	$118.58	$118.60	$118.60
Purchase #4	$71.99	4.236%	$75.0395	$75.04	$75.05	$75.00
Purchase #5	$181.85	5.826%	$192.4446	$192.44	$192.45	$192.40
Purchase #6	$74.27	4.469%	$77.5891	$77.59	$77.60	$77.60
Purchase #7	$95.59	4.780%	$100.1592	$100.16	$100.15	$100.20
7 purchase totals =	$833.08		$892.2052	$892.21	$892.25	$892.20