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	$197.86	11.180%	$219.9807	$219.98	$220.00	$220.00
Purchase #2	$225.43	11.186%	$250.6466	$250.65	$250.65	$250.60
Purchase #3	$52.38	3.110%	$54.009	$54.01	$54.00	$54.00
Purchase #4	$244.43	13.251%	$276.8194	$276.82	$276.80	$276.80
Purchase #5	$40.46	6.109%	$42.9317	$42.93	$42.95	$42.90
Purchase #6	$207.76	11.434%	$231.5153	$231.52	$231.50	$231.50
Purchase #7	$12.69	4.491%	$13.2599	$13.26	$13.25	$13.30
7 purchase totals =	$981.01		$1,089.1626	$1,089.17	$1,089.15	$1,089.10