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	$170.59	7.632%	$183.6094	$183.61	$183.60	$183.60
Purchase #2	$79.74	3.490%	$82.5229	$82.52	$82.50	$82.50
Purchase #3	$167.90	3.271%	$173.392	$173.39	$173.40	$173.40
Purchase #4	$44.91	12.264%	$50.4178	$50.42	$50.40	$50.40
Purchase #5	$62.28	7.849%	$67.1684	$67.17	$67.15	$67.20
Purchase #6	$11.78	6.415%	$12.5357	$12.54	$12.55	$12.50
Purchase #7	$116.42	11.694%	$130.0342	$130.03	$130.05	$130.00
7 purchase totals =	$653.62		$699.6804	$699.68	$699.65	$699.60