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	$172.84	4.185%	$180.0734	$180.07	$180.05	$180.10
Purchase #2	$144.94	3.665%	$150.2521	$150.25	$150.25	$150.30
Purchase #3	$75.95	3.421%	$78.5482	$78.55	$78.55	$78.50
Purchase #4	$247.29	12.516%	$278.2408	$278.24	$278.25	$278.20
Purchase #5	$194.43	6.643%	$207.346	$207.35	$207.35	$207.30
Purchase #6	$146.28	3.309%	$151.1204	$151.12	$151.10	$151.10
Purchase #7	$143.98	4.584%	$150.58	$150.58	$150.60	$150.60
7 purchase totals =	$1,125.71		$1,196.1609	$1,196.16	$1,196.15	$1,196.10