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	$181.73	3.604%	$188.2795	$188.28	$188.30	$188.30
Purchase #2	$73.45	6.572%	$78.2771	$78.28	$78.30	$78.30
Purchase #3	$95.64	12.852%	$107.9317	$107.93	$107.95	$107.90
Purchase #4	$44.33	7.389%	$47.6055	$47.61	$47.60	$47.60
Purchase #5	$28.31	5.180%	$29.7765	$29.78	$29.80	$29.80
Purchase #6	$115.48	13.847%	$131.4705	$131.47	$131.45	$131.50
Purchase #7	$165.53	4.177%	$172.4442	$172.44	$172.45	$172.40
7 purchase totals =	$704.47		$755.7850	$755.79	$755.85	$755.80