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	$146.51	6.702%	$156.3291	$156.33	$156.35	$156.30
Purchase #2	$19.51	10.230%	$21.5059	$21.51	$21.50	$21.50
Purchase #3	$224.96	6.130%	$238.75	$238.75	$238.75	$238.80
Purchase #4	$123.30	3.130%	$127.1593	$127.16	$127.15	$127.20
Purchase #5	$217.87	7.269%	$233.707	$233.71	$233.70	$233.70
Purchase #6	$151.70	6.532%	$161.609	$161.61	$161.60	$161.60
Purchase #7	$221.45	11.722%	$247.4084	$247.41	$247.40	$247.40
7 purchase totals =	$1,105.30		$1,186.4687	$1,186.48	$1,186.45	$1,186.50