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	$206.79	11.496%	$230.5626	$230.56	$230.55	$230.60
Purchase #2	$173.45	13.438%	$196.7582	$196.76	$196.75	$196.80
Purchase #3	$64.68	3.634%	$67.0305	$67.03	$67.05	$67.00
Purchase #4	$144.85	7.793%	$156.1382	$156.14	$156.15	$156.10
Purchase #5	$240.45	3.843%	$249.6905	$249.69	$249.70	$249.70
Purchase #6	$66.77	5.152%	$70.21	$70.21	$70.20	$70.20
Purchase #7	$45.95	10.141%	$50.6098	$50.61	$50.60	$50.60
7 purchase totals =	$942.94		$1,020.9998	$1,021.00	$1,021.00	$1,021.00