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	$136.54	6.551%	$145.4847	$145.48	$145.50	$145.50
Purchase #2	$223.26	13.231%	$252.7995	$252.80	$252.80	$252.80
Purchase #3	$103.36	5.377%	$108.9177	$108.92	$108.90	$108.90
Purchase #4	$230.82	9.722%	$253.2603	$253.26	$253.25	$253.30
Purchase #5	$97.42	12.800%	$109.8898	$109.89	$109.90	$109.90
Purchase #6	$111.32	13.634%	$126.4974	$126.50	$126.50	$126.50
Purchase #7	$51.74	3.828%	$53.7206	$53.72	$53.70	$53.70
7 purchase totals =	$954.46		$1,050.5700	$1,050.57	$1,050.55	$1,050.60