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	$106.92	4.319%	$111.5379	$111.54	$111.55	$111.50
Purchase #2	$87.60	4.385%	$91.4413	$91.44	$91.45	$91.40
Purchase #3	$190.70	5.454%	$201.1008	$201.10	$201.10	$201.10
Purchase #4	$184.66	13.532%	$209.6482	$209.65	$209.65	$209.60
Purchase #5	$33.60	4.634%	$35.157	$35.16	$35.15	$35.20
Purchase #6	$142.77	9.565%	$156.426	$156.43	$156.45	$156.40
Purchase #7	$141.52	8.521%	$153.5789	$153.58	$153.60	$153.60
7 purchase totals =	$887.77		$958.8901	$958.90	$958.95	$958.80