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	$97.89	6.188%	$103.9474	$103.95	$103.95	$103.90
Purchase #2	$238.44	8.846%	$259.5324	$259.53	$259.55	$259.50
Purchase #3	$37.28	9.513%	$40.8264	$40.83	$40.85	$40.80
Purchase #4	$143.58	5.501%	$151.4783	$151.48	$151.50	$151.50
Purchase #5	$77.30	7.762%	$83.3	$83.30	$83.30	$83.30
Purchase #6	$15.42	12.184%	$17.2988	$17.30	$17.30	$17.30
Purchase #7	$165.89	4.868%	$173.9655	$173.97	$173.95	$174.00
7 purchase totals =	$775.80		$830.3488	$830.36	$830.40	$830.30