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	$222.58	6.719%	$237.5352	$237.54	$237.55	$237.50
Purchase #2	$176.54	8.598%	$191.7189	$191.72	$191.70	$191.70
Purchase #3	$192.81	12.756%	$217.4048	$217.40	$217.40	$217.40
Purchase #4	$56.72	4.779%	$59.4306	$59.43	$59.45	$59.40
Purchase #5	$89.67	12.800%	$101.1478	$101.15	$101.15	$101.10
Purchase #6	$206.84	11.333%	$230.2812	$230.28	$230.30	$230.30
Purchase #7	$122.87	6.400%	$130.7337	$130.73	$130.75	$130.70
7 purchase totals =	$1,068.03		$1,168.2522	$1,168.25	$1,168.30	$1,168.10