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	$179.98	4.184%	$187.5104	$187.51	$187.50	$187.50
Purchase #2	$59.50	7.845%	$64.1678	$64.17	$64.15	$64.20
Purchase #3	$12.27	13.392%	$13.9132	$13.91	$13.90	$13.90
Purchase #4	$238.39	3.718%	$247.2533	$247.25	$247.25	$247.30
Purchase #5	$249.60	9.259%	$272.7105	$272.71	$272.70	$272.70
Purchase #6	$51.52	5.174%	$54.1856	$54.19	$54.20	$54.20
Purchase #7	$209.56	5.678%	$221.4588	$221.46	$221.45	$221.50
7 purchase totals =	$1,000.82		$1,061.1996	$1,061.20	$1,061.15	$1,061.30