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	$204.46	9.538%	$223.9614	$223.96	$223.95	$224.00
Purchase #2	$60.45	8.141%	$65.3712	$65.37	$65.35	$65.40
Purchase #3	$165.63	12.130%	$185.7209	$185.72	$185.70	$185.70
Purchase #4	$10.92	12.465%	$12.2812	$12.28	$12.30	$12.30
Purchase #5	$180.58	3.419%	$186.754	$186.75	$186.75	$186.80
Purchase #6	$93.84	12.793%	$105.845	$105.85	$105.85	$105.80
Purchase #7	$59.80	11.451%	$66.6477	$66.65	$66.65	$66.60
7 purchase totals =	$775.68		$846.5814	$846.58	$846.55	$846.60