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	$242.45	7.862%	$261.5114	$261.51	$261.50	$261.50
Purchase #2	$144.98	4.198%	$151.0663	$151.07	$151.05	$151.10
Purchase #3	$50.46	8.856%	$54.9287	$54.93	$54.95	$54.90
Purchase #4	$23.52	4.440%	$24.5643	$24.56	$24.55	$24.60
Purchase #5	$94.48	8.247%	$102.2718	$102.27	$102.25	$102.30
Purchase #6	$122.92	3.735%	$127.5111	$127.51	$127.50	$127.50
Purchase #7	$53.49	12.705%	$60.2859	$60.29	$60.30	$60.30
7 purchase totals =	$732.30		$782.1395	$782.14	$782.10	$782.20