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	$144.69	9.707%	$158.7351	$158.74	$158.75	$158.70
Purchase #2	$208.56	4.422%	$217.7825	$217.78	$217.80	$217.80
Purchase #3	$249.63	6.668%	$266.2753	$266.28	$266.30	$266.30
Purchase #4	$186.47	5.462%	$196.655	$196.66	$196.65	$196.70
Purchase #5	$90.93	9.660%	$99.7138	$99.71	$99.70	$99.70
Purchase #6	$160.69	7.868%	$173.3331	$173.33	$173.35	$173.30
Purchase #7	$118.92	3.558%	$123.1512	$123.15	$123.15	$123.20
7 purchase totals =	$1,159.89		$1,235.6460	$1,235.65	$1,235.70	$1,235.70