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	$88.48	4.858%	$92.7784	$92.78	$92.80	$92.80
Purchase #2	$111.99	10.141%	$123.3469	$123.35	$123.35	$123.30
Purchase #3	$18.90	13.146%	$21.3846	$21.38	$21.40	$21.40
Purchase #4	$94.46	5.688%	$99.8329	$99.83	$99.85	$99.80
Purchase #5	$24.30	11.660%	$27.1334	$27.13	$27.15	$27.10
Purchase #6	$41.56	9.773%	$45.6217	$45.62	$45.60	$45.60
Purchase #7	$33.35	8.782%	$36.2788	$36.28	$36.30	$36.30
7 purchase totals =	$413.04		$446.3767	$446.37	$446.45	$446.30