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	$128.54	12.455%	$144.5497	$144.55	$144.55	$144.50
Purchase #2	$104.82	13.127%	$118.5797	$118.58	$118.60	$118.60
Purchase #3	$193.48	10.727%	$214.2346	$214.23	$214.25	$214.20
Purchase #4	$61.52	4.115%	$64.0515	$64.05	$64.05	$64.10
Purchase #5	$159.40	3.585%	$165.1145	$165.11	$165.10	$165.10
Purchase #6	$244.40	5.509%	$257.864	$257.86	$257.85	$257.90
Purchase #7	$47.50	6.859%	$50.758	$50.76	$50.75	$50.80
7 purchase totals =	$939.66		$1,015.1520	$1,015.14	$1,015.15	$1,015.20