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	$83.77	10.714%	$92.7451	$92.75	$92.75	$92.70
Purchase #2	$153.58	4.278%	$160.1502	$160.15	$160.15	$160.20
Purchase #3	$56.82	4.482%	$59.3667	$59.37	$59.35	$59.40
Purchase #4	$70.32	10.264%	$77.5376	$77.54	$77.55	$77.50
Purchase #5	$98.36	13.282%	$111.4242	$111.42	$111.40	$111.40
Purchase #6	$171.71	12.843%	$193.7627	$193.76	$193.75	$193.80
Purchase #7	$118.61	10.283%	$130.8067	$130.81	$130.80	$130.80
7 purchase totals =	$753.17		$825.7932	$825.80	$825.75	$825.80