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	$38.35	13.543%	$43.5437	$43.54	$43.55	$43.50
Purchase #2	$151.52	3.719%	$157.155	$157.16	$157.15	$157.20
Purchase #3	$166.85	12.832%	$188.2602	$188.26	$188.25	$188.30
Purchase #4	$96.56	9.463%	$105.6975	$105.70	$105.70	$105.70
Purchase #5	$239.69	13.554%	$272.1776	$272.18	$272.20	$272.20
Purchase #6	$244.29	9.514%	$267.5318	$267.53	$267.55	$267.50
Purchase #7	$93.42	4.366%	$97.4987	$97.50	$97.50	$97.50
7 purchase totals =	$1,030.68		$1,131.8645	$1,131.87	$1,131.90	$1,131.90