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	$45.59	9.287%	$49.8239	$49.82	$49.80	$49.80
Purchase #2	$164.77	4.585%	$172.3247	$172.32	$172.30	$172.30
Purchase #3	$54.59	9.248%	$59.6385	$59.64	$59.65	$59.60
Purchase #4	$182.70	4.155%	$190.2912	$190.29	$190.30	$190.30
Purchase #5	$143.42	12.288%	$161.0434	$161.04	$161.05	$161.00
Purchase #6	$106.27	5.756%	$112.3869	$112.39	$112.40	$112.40
Purchase #7	$132.31	3.637%	$137.1221	$137.12	$137.10	$137.10
7 purchase totals =	$829.65		$882.6307	$882.62	$882.60	$882.50