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	$153.28	3.323%	$158.3735	$158.37	$158.35	$158.40
Purchase #2	$187.94	13.659%	$213.6107	$213.61	$213.60	$213.60
Purchase #3	$44.89	13.227%	$50.8276	$50.83	$50.85	$50.80
Purchase #4	$35.38	5.361%	$37.2767	$37.28	$37.30	$37.30
Purchase #5	$166.47	4.328%	$173.6748	$173.67	$173.65	$173.70
Purchase #6	$214.70	5.499%	$226.5064	$226.51	$226.50	$226.50
Purchase #7	$18.31	12.388%	$20.5782	$20.58	$20.60	$20.60
7 purchase totals =	$820.97		$880.8479	$880.85	$880.85	$880.90