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	$200.27	9.442%	$219.1795	$219.18	$219.20	$219.20
Purchase #2	$157.70	9.440%	$172.5869	$172.59	$172.60	$172.60
Purchase #3	$77.66	6.382%	$82.6163	$82.62	$82.60	$82.60
Purchase #4	$230.86	10.576%	$255.2758	$255.28	$255.30	$255.30
Purchase #5	$66.86	9.647%	$73.31	$73.31	$73.30	$73.30
Purchase #6	$122.36	5.857%	$129.5266	$129.53	$129.55	$129.50
Purchase #7	$209.47	12.341%	$235.3207	$235.32	$235.30	$235.30
7 purchase totals =	$1,065.18		$1,167.8158	$1,167.83	$1,167.85	$1,167.80