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	$221.59	5.513%	$233.8063	$233.81	$233.80	$233.80
Purchase #2	$43.90	3.655%	$45.5045	$45.50	$45.50	$45.50
Purchase #3	$229.43	7.120%	$245.7654	$245.77	$245.75	$245.80
Purchase #4	$246.49	9.262%	$269.3199	$269.32	$269.30	$269.30
Purchase #5	$67.71	3.573%	$70.1293	$70.13	$70.15	$70.10
Purchase #6	$44.63	13.551%	$50.6778	$50.68	$50.70	$50.70
Purchase #7	$145.82	8.677%	$158.4728	$158.47	$158.45	$158.50
7 purchase totals =	$999.57		$1,073.6760	$1,073.68	$1,073.65	$1,073.70