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	$92.60	13.472%	$105.0751	$105.08	$105.10	$105.10
Purchase #2	$19.46	10.504%	$21.5041	$21.50	$21.50	$21.50
Purchase #3	$12.66	4.860%	$13.2753	$13.28	$13.30	$13.30
Purchase #4	$33.29	13.204%	$37.6856	$37.69	$37.70	$37.70
Purchase #5	$224.56	12.757%	$253.2071	$253.21	$253.20	$253.20
Purchase #6	$83.97	3.166%	$86.6285	$86.63	$86.65	$86.60
Purchase #7	$151.69	4.298%	$158.2096	$158.21	$158.20	$158.20
7 purchase totals =	$618.23		$675.5853	$675.60	$675.65	$675.60