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	$122.66	3.666%	$127.1567	$127.16	$127.15	$127.20
Purchase #2	$61.52	8.342%	$66.652	$66.65	$66.65	$66.70
Purchase #3	$146.75	13.484%	$166.5378	$166.54	$166.55	$166.50
Purchase #4	$230.55	11.820%	$257.801	$257.80	$257.80	$257.80
Purchase #5	$188.50	11.600%	$210.366	$210.37	$210.35	$210.40
Purchase #6	$165.72	8.560%	$179.9056	$179.91	$179.90	$179.90
Purchase #7	$151.75	4.566%	$158.6789	$158.68	$158.70	$158.70
7 purchase totals =	$1,067.45		$1,167.0980	$1,167.11	$1,167.10	$1,167.20