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	$198.78	11.812%	$222.2599	$222.26	$222.25	$222.30
Purchase #2	$188.75	13.442%	$214.1218	$214.12	$214.10	$214.10
Purchase #3	$140.43	5.237%	$147.7843	$147.78	$147.80	$147.80
Purchase #4	$238.77	6.756%	$254.9013	$254.90	$254.90	$254.90
Purchase #5	$227.32	3.569%	$235.4331	$235.43	$235.45	$235.40
Purchase #6	$233.51	9.658%	$256.0624	$256.06	$256.05	$256.10
Purchase #7	$88.71	13.631%	$100.8021	$100.80	$100.80	$100.80
7 purchase totals =	$1,316.27		$1,431.3649	$1,431.35	$1,431.35	$1,431.40