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	$36.41	10.844%	$40.3583	$40.36	$40.35	$40.40
Purchase #2	$88.58	10.466%	$97.8508	$97.85	$97.85	$97.90
Purchase #3	$120.87	9.343%	$132.1629	$132.16	$132.15	$132.20
Purchase #4	$46.42	13.555%	$52.7122	$52.71	$52.70	$52.70
Purchase #5	$42.38	7.768%	$45.6721	$45.67	$45.65	$45.70
Purchase #6	$157.52	10.117%	$173.4563	$173.46	$173.45	$173.50
Purchase #7	$155.60	10.503%	$171.9427	$171.94	$171.95	$171.90
7 purchase totals =	$647.78		$714.1553	$714.15	$714.10	$714.30