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	$114.73	10.823%	$127.1472	$127.15	$127.15	$127.10
Purchase #2	$55.92	12.520%	$62.9212	$62.92	$62.90	$62.90
Purchase #3	$24.48	4.260%	$25.5228	$25.52	$25.50	$25.50
Purchase #4	$15.47	12.293%	$17.3717	$17.37	$17.35	$17.40
Purchase #5	$20.81	7.819%	$22.4371	$22.44	$22.45	$22.40
Purchase #6	$206.69	13.213%	$233.9999	$234.00	$234.00	$234.00
Purchase #7	$40.37	8.712%	$43.887	$43.89	$43.90	$43.90
7 purchase totals =	$478.47		$533.2869	$533.29	$533.25	$533.20