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	$73.26	7.590%	$78.8204	$78.82	$78.80	$78.80
Purchase #2	$71.57	8.643%	$77.7558	$77.76	$77.75	$77.80
Purchase #3	$45.98	8.801%	$50.0267	$50.03	$50.05	$50.00
Purchase #4	$101.43	10.102%	$111.6765	$111.68	$111.70	$111.70
Purchase #5	$147.93	5.766%	$156.4596	$156.46	$156.45	$156.50
Purchase #6	$225.31	5.637%	$238.0107	$238.01	$238.00	$238.00
Purchase #7	$10.26	10.354%	$11.3223	$11.32	$11.30	$11.30
7 purchase totals =	$675.74		$724.0720	$724.08	$724.05	$724.10