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	$179.50	7.773%	$193.4525	$193.45	$193.45	$193.50
Purchase #2	$119.85	7.302%	$128.6014	$128.60	$128.60	$128.60
Purchase #3	$54.37	9.847%	$59.7238	$59.72	$59.70	$59.70
Purchase #4	$173.83	11.261%	$193.405	$193.41	$193.40	$193.40
Purchase #5	$159.80	12.140%	$179.1997	$179.20	$179.20	$179.20
Purchase #6	$52.83	5.315%	$55.6379	$55.64	$55.65	$55.60
Purchase #7	$224.45	4.825%	$235.2797	$235.28	$235.30	$235.30
7 purchase totals =	$964.63		$1,045.3000	$1,045.30	$1,045.30	$1,045.30