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	$30.85	5.543%	$32.56	$32.56	$32.55	$32.60
Purchase #2	$158.92	9.254%	$173.6265	$173.63	$173.65	$173.60
Purchase #3	$104.87	6.556%	$111.7453	$111.75	$111.75	$111.70
Purchase #4	$125.60	10.489%	$138.7742	$138.77	$138.75	$138.80
Purchase #5	$213.70	4.603%	$223.5366	$223.54	$223.55	$223.50
Purchase #6	$97.93	7.144%	$104.9261	$104.93	$104.95	$104.90
Purchase #7	$37.94	12.172%	$42.5581	$42.56	$42.55	$42.60
7 purchase totals =	$769.81		$827.7268	$827.74	$827.75	$827.70