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	$176.34	8.658%	$191.6075	$191.61	$191.60	$191.60
Purchase #2	$121.41	13.575%	$137.8914	$137.89	$137.90	$137.90
Purchase #3	$153.47	12.738%	$173.019	$173.02	$173.00	$173.00
Purchase #4	$219.46	12.241%	$246.3241	$246.32	$246.30	$246.30
Purchase #5	$178.84	6.656%	$190.7436	$190.74	$190.75	$190.70
Purchase #6	$17.89	8.552%	$19.42	$19.42	$19.40	$19.40
Purchase #7	$43.53	5.176%	$45.7831	$45.78	$45.80	$45.80
7 purchase totals =	$910.94		$1,004.7887	$1,004.78	$1,004.75	$1,004.70