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	$147.49	9.512%	$161.5192	$161.52	$161.50	$161.50
Purchase #2	$235.95	11.646%	$263.4287	$263.43	$263.45	$263.40
Purchase #3	$136.33	11.533%	$152.0529	$152.05	$152.05	$152.10
Purchase #4	$132.33	8.161%	$143.1295	$143.13	$143.15	$143.10
Purchase #5	$159.56	8.174%	$172.6024	$172.60	$172.60	$172.60
Purchase #6	$72.70	7.734%	$78.3226	$78.32	$78.30	$78.30
Purchase #7	$225.54	10.612%	$249.4743	$249.47	$249.45	$249.50
7 purchase totals =	$1,109.90		$1,220.5296	$1,220.52	$1,220.50	$1,220.50