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	$230.74	8.202%	$249.6653	$249.67	$249.65	$249.70
Purchase #2	$158.83	11.267%	$176.7254	$176.73	$176.75	$176.70
Purchase #3	$173.57	6.737%	$185.2634	$185.26	$185.25	$185.30
Purchase #4	$153.69	8.344%	$166.5139	$166.51	$166.50	$166.50
Purchase #5	$72.80	11.660%	$81.2885	$81.29	$81.30	$81.30
Purchase #6	$32.99	3.468%	$34.1341	$34.13	$34.15	$34.10
Purchase #7	$147.25	13.825%	$167.6073	$167.61	$167.60	$167.60
7 purchase totals =	$969.87		$1,061.1979	$1,061.20	$1,061.20	$1,061.20