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	$177.75	10.288%	$196.0369	$196.04	$196.05	$196.00
Purchase #2	$158.39	11.843%	$177.1481	$177.15	$177.15	$177.10
Purchase #3	$118.68	4.198%	$123.6622	$123.66	$123.65	$123.70
Purchase #4	$10.54	9.265%	$11.5165	$11.52	$11.50	$11.50
Purchase #5	$145.27	5.566%	$153.3557	$153.36	$153.35	$153.40
Purchase #6	$52.71	13.318%	$59.7299	$59.73	$59.75	$59.70
Purchase #7	$247.50	11.546%	$276.0764	$276.08	$276.10	$276.10
7 purchase totals =	$910.84		$997.5257	$997.54	$997.55	$997.50