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	$250.71	4.650%	$262.368	$262.37	$262.35	$262.40
Purchase #2	$149.26	11.413%	$166.295	$166.30	$166.30	$166.30
Purchase #3	$129.76	13.174%	$146.8546	$146.85	$146.85	$146.90
Purchase #4	$30.92	5.696%	$32.6812	$32.68	$32.70	$32.70
Purchase #5	$99.93	11.222%	$111.1441	$111.14	$111.15	$111.10
Purchase #6	$122.98	6.674%	$131.1877	$131.19	$131.20	$131.20
Purchase #7	$42.86	4.723%	$44.8843	$44.88	$44.90	$44.90
7 purchase totals =	$826.42		$895.4149	$895.41	$895.45	$895.50