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	$233.84	8.780%	$254.3712	$254.37	$254.35	$254.40
Purchase #2	$117.66	8.439%	$127.5893	$127.59	$127.60	$127.60
Purchase #3	$151.64	3.726%	$157.2901	$157.29	$157.30	$157.30
Purchase #4	$162.71	13.237%	$184.2479	$184.25	$184.25	$184.20
Purchase #5	$117.87	7.873%	$127.1499	$127.15	$127.15	$127.10
Purchase #6	$54.52	11.466%	$60.7713	$60.77	$60.75	$60.80
Purchase #7	$236.29	13.396%	$267.9434	$267.94	$267.95	$267.90
7 purchase totals =	$1,074.53		$1,179.3631	$1,179.36	$1,179.35	$1,179.30