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	$212.99	8.581%	$231.2667	$231.27	$231.25	$231.30
Purchase #2	$233.92	4.369%	$244.14	$244.14	$244.15	$244.10
Purchase #3	$172.41	10.558%	$190.613	$190.61	$190.60	$190.60
Purchase #4	$137.73	4.786%	$144.3218	$144.32	$144.30	$144.30
Purchase #5	$156.84	6.660%	$167.2855	$167.29	$167.30	$167.30
Purchase #6	$162.91	11.743%	$182.0405	$182.04	$182.05	$182.00
Purchase #7	$10.92	7.388%	$11.7268	$11.73	$11.75	$11.70
7 purchase totals =	$1,087.72		$1,171.3943	$1,171.40	$1,171.40	$1,171.30