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	$77.27	11.212%	$85.9335	$85.93	$85.95	$85.90
Purchase #2	$198.93	12.441%	$223.6789	$223.68	$223.70	$223.70
Purchase #3	$15.84	7.697%	$17.0592	$17.06	$17.05	$17.10
Purchase #4	$73.45	6.419%	$78.1648	$78.16	$78.15	$78.20
Purchase #5	$132.72	8.608%	$144.1445	$144.14	$144.15	$144.10
Purchase #6	$74.85	8.179%	$80.972	$80.97	$80.95	$81.00
Purchase #7	$179.30	9.733%	$196.7513	$196.75	$196.75	$196.80
7 purchase totals =	$752.36		$826.7042	$826.69	$826.70	$826.80