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	$158.50	13.226%	$179.4632	$179.46	$179.45	$179.50
Purchase #2	$74.94	4.848%	$78.5731	$78.57	$78.55	$78.60
Purchase #3	$143.99	9.312%	$157.3983	$157.40	$157.40	$157.40
Purchase #4	$209.25	10.698%	$231.6356	$231.64	$231.65	$231.60
Purchase #5	$175.29	3.424%	$181.2919	$181.29	$181.30	$181.30
Purchase #6	$26.44	6.163%	$28.0695	$28.07	$28.05	$28.10
Purchase #7	$151.74	5.414%	$159.9552	$159.96	$159.95	$160.00
7 purchase totals =	$940.15		$1,016.3868	$1,016.39	$1,016.35	$1,016.50