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	$177.25	4.645%	$185.4833	$185.48	$185.50	$185.50
Purchase #2	$227.81	10.417%	$251.541	$251.54	$251.55	$251.50
Purchase #3	$230.72	13.697%	$262.3217	$262.32	$262.30	$262.30
Purchase #4	$115.66	12.528%	$130.1499	$130.15	$130.15	$130.10
Purchase #5	$71.43	11.268%	$79.4787	$79.48	$79.50	$79.50
Purchase #6	$243.51	9.766%	$267.2912	$267.29	$267.30	$267.30
Purchase #7	$239.87	11.343%	$267.0785	$267.08	$267.10	$267.10
7 purchase totals =	$1,306.25		$1,443.3443	$1,443.34	$1,443.40	$1,443.30