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	$124.68	4.130%	$129.8293	$129.83	$129.85	$129.80
Purchase #2	$79.52	13.407%	$90.1812	$90.18	$90.20	$90.20
Purchase #3	$63.29	5.603%	$66.8361	$66.84	$66.85	$66.80
Purchase #4	$214.65	13.274%	$243.1426	$243.14	$243.15	$243.10
Purchase #5	$38.76	11.244%	$43.1182	$43.12	$43.10	$43.10
Purchase #6	$185.31	4.845%	$194.2883	$194.29	$194.30	$194.30
Purchase #7	$216.72	11.452%	$241.5388	$241.54	$241.55	$241.50
7 purchase totals =	$922.93		$1,008.9345	$1,008.94	$1,009.00	$1,008.80