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	$71.68	7.561%	$77.0997	$77.10	$77.10	$77.10
Purchase #2	$107.57	3.849%	$111.7104	$111.71	$111.70	$111.70
Purchase #3	$93.72	12.530%	$105.4631	$105.46	$105.45	$105.50
Purchase #4	$69.87	10.139%	$76.9541	$76.95	$76.95	$77.00
Purchase #5	$9.50	6.270%	$10.0957	$10.10	$10.10	$10.10
Purchase #6	$168.76	8.872%	$183.7324	$183.73	$183.75	$183.70
Purchase #7	$113.76	4.357%	$118.7165	$118.72	$118.70	$118.70
7 purchase totals =	$634.86		$683.7719	$683.77	$683.75	$683.80