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	$141.91	11.528%	$158.2694	$158.27	$158.25	$158.30
Purchase #2	$213.50	4.275%	$222.6271	$222.63	$222.65	$222.60
Purchase #3	$246.27	13.462%	$279.4229	$279.42	$279.40	$279.40
Purchase #4	$46.75	11.512%	$52.1319	$52.13	$52.15	$52.10
Purchase #5	$155.34	4.771%	$162.7513	$162.75	$162.75	$162.80
Purchase #6	$30.61	4.849%	$32.0943	$32.09	$32.10	$32.10
Purchase #7	$151.85	5.825%	$160.6953	$160.70	$160.70	$160.70
7 purchase totals =	$986.23		$1,067.9922	$1,067.99	$1,068.00	$1,068.00