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	$35.69	8.336%	$38.6651	$38.67	$38.65	$38.70
Purchase #2	$48.30	13.639%	$54.8876	$54.89	$54.90	$54.90
Purchase #3	$185.76	5.494%	$195.9657	$195.97	$195.95	$196.00
Purchase #4	$133.27	13.353%	$151.0655	$151.07	$151.05	$151.10
Purchase #5	$173.37	12.719%	$195.4209	$195.42	$195.40	$195.40
Purchase #6	$250.57	10.468%	$276.7997	$276.80	$276.80	$276.80
Purchase #7	$98.86	6.796%	$105.5785	$105.58	$105.60	$105.60
7 purchase totals =	$925.82		$1,018.3830	$1,018.40	$1,018.35	$1,018.50