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	$219.68	3.754%	$227.9268	$227.93	$227.95	$227.90
Purchase #2	$37.75	4.552%	$39.4684	$39.47	$39.45	$39.50
Purchase #3	$132.52	10.388%	$146.2862	$146.29	$146.30	$146.30
Purchase #4	$228.34	9.126%	$249.1783	$249.18	$249.20	$249.20
Purchase #5	$36.81	3.668%	$38.1602	$38.16	$38.15	$38.20
Purchase #6	$157.77	9.372%	$172.5562	$172.56	$172.55	$172.60
Purchase #7	$40.93	11.294%	$45.5526	$45.55	$45.55	$45.60
7 purchase totals =	$853.80		$919.1287	$919.14	$919.15	$919.30