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	$204.47	5.169%	$215.0391	$215.04	$215.05	$215.00
Purchase #2	$87.42	4.582%	$91.4256	$91.43	$91.45	$91.40
Purchase #3	$237.68	11.219%	$264.3453	$264.35	$264.35	$264.30
Purchase #4	$46.85	13.387%	$53.1218	$53.12	$53.10	$53.10
Purchase #5	$172.49	9.206%	$188.3694	$188.37	$188.35	$188.40
Purchase #6	$138.52	4.827%	$145.2064	$145.21	$145.20	$145.20
Purchase #7	$216.72	10.308%	$239.0595	$239.06	$239.05	$239.10
7 purchase totals =	$1,104.15		$1,196.5671	$1,196.58	$1,196.55	$1,196.50