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	$188.49	6.139%	$200.0614	$200.06	$200.05	$200.10
Purchase #2	$214.55	12.842%	$242.1025	$242.10	$242.10	$242.10
Purchase #3	$66.87	5.393%	$70.4763	$70.48	$70.50	$70.50
Purchase #4	$229.96	9.498%	$251.8016	$251.80	$251.80	$251.80
Purchase #5	$41.65	4.700%	$43.6076	$43.61	$43.60	$43.60
Purchase #6	$62.58	8.501%	$67.8999	$67.90	$67.90	$67.90
Purchase #7	$226.40	13.137%	$256.1422	$256.14	$256.15	$256.10
7 purchase totals =	$1,030.50		$1,132.0915	$1,132.09	$1,132.10	$1,132.10