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	$148.27	11.388%	$165.155	$165.16	$165.15	$165.20
Purchase #2	$156.62	13.668%	$178.0268	$178.03	$178.05	$178.00
Purchase #3	$139.84	8.472%	$151.6872	$151.69	$151.70	$151.70
Purchase #4	$213.32	4.793%	$223.5444	$223.54	$223.55	$223.50
Purchase #5	$35.74	13.541%	$40.5796	$40.58	$40.60	$40.60
Purchase #6	$94.98	6.644%	$101.2905	$101.29	$101.30	$101.30
Purchase #7	$5.40	3.150%	$5.5701	$5.57	$5.55	$5.60
7 purchase totals =	$794.17		$865.8536	$865.86	$865.90	$865.90