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	$177.27	13.325%	$200.8912	$200.89	$200.90	$200.90
Purchase #2	$121.54	12.463%	$136.6875	$136.69	$136.70	$136.70
Purchase #3	$234.55	3.259%	$242.194	$242.19	$242.20	$242.20
Purchase #4	$158.39	4.585%	$165.6522	$165.65	$165.65	$165.70
Purchase #5	$140.35	4.578%	$146.7752	$146.78	$146.80	$146.80
Purchase #6	$234.44	6.745%	$250.253	$250.25	$250.25	$250.30
Purchase #7	$237.87	7.461%	$255.6175	$255.62	$255.60	$255.60
7 purchase totals =	$1,304.41		$1,398.0706	$1,398.07	$1,398.10	$1,398.20