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	$175.83	5.262%	$185.0822	$185.08	$185.10	$185.10
Purchase #2	$31.55	7.683%	$33.974	$33.97	$33.95	$34.00
Purchase #3	$110.62	11.433%	$123.2672	$123.27	$123.25	$123.30
Purchase #4	$238.35	7.358%	$255.8878	$255.89	$255.90	$255.90
Purchase #5	$54.91	4.368%	$57.3085	$57.31	$57.30	$57.30
Purchase #6	$100.26	5.393%	$105.667	$105.67	$105.65	$105.70
Purchase #7	$192.62	4.563%	$201.4093	$201.41	$201.40	$201.40
7 purchase totals =	$904.14		$962.5960	$962.60	$962.55	$962.70