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	$115.83	6.763%	$123.6636	$123.66	$123.65	$123.70
Purchase #2	$116.76	9.498%	$127.8499	$127.85	$127.85	$127.80
Purchase #3	$221.80	3.697%	$229.9999	$230.00	$230.00	$230.00
Purchase #4	$17.93	4.294%	$18.6999	$18.70	$18.70	$18.70
Purchase #5	$9.42	13.128%	$10.6567	$10.66	$10.65	$10.70
Purchase #6	$244.46	3.656%	$253.3975	$253.40	$253.40	$253.40
Purchase #7	$249.35	10.489%	$275.5043	$275.50	$275.50	$275.50
7 purchase totals =	$975.55		$1,039.7718	$1,039.77	$1,039.75	$1,039.80