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	$207.34	8.759%	$225.5009	$225.50	$225.50	$225.50
Purchase #2	$78.25	4.158%	$81.5036	$81.50	$81.50	$81.50
Purchase #3	$127.41	9.525%	$139.5458	$139.55	$139.55	$139.50
Purchase #4	$234.91	6.500%	$250.1792	$250.18	$250.20	$250.20
Purchase #5	$12.37	3.308%	$12.7792	$12.78	$12.80	$12.80
Purchase #6	$47.31	10.226%	$52.1479	$52.15	$52.15	$52.10
Purchase #7	$30.52	13.607%	$34.6729	$34.67	$34.65	$34.70
7 purchase totals =	$738.11		$796.3295	$796.33	$796.35	$796.30