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	$158.82	4.431%	$165.8573	$165.86	$165.85	$165.90
Purchase #2	$82.56	11.766%	$92.274	$92.27	$92.25	$92.30
Purchase #3	$214.60	7.551%	$230.8044	$230.80	$230.80	$230.80
Purchase #4	$221.44	4.639%	$231.7126	$231.71	$231.70	$231.70
Purchase #5	$96.50	5.644%	$101.9465	$101.95	$101.95	$101.90
Purchase #6	$247.26	3.294%	$255.4047	$255.40	$255.40	$255.40
Purchase #7	$148.69	12.656%	$167.5082	$167.51	$167.50	$167.50
7 purchase totals =	$1,169.87		$1,245.5077	$1,245.50	$1,245.45	$1,245.50