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	$43.78	4.468%	$45.7361	$45.74	$45.75	$45.70
Purchase #2	$48.77	5.540%	$51.4719	$51.47	$51.45	$51.50
Purchase #3	$177.79	6.472%	$189.2966	$189.30	$189.30	$189.30
Purchase #4	$147.94	7.261%	$158.6819	$158.68	$158.70	$158.70
Purchase #5	$41.46	9.557%	$45.4223	$45.42	$45.40	$45.40
Purchase #6	$25.85	6.128%	$27.4341	$27.43	$27.45	$27.40
Purchase #7	$85.83	7.714%	$92.4509	$92.45	$92.45	$92.50
7 purchase totals =	$571.42		$610.4938	$610.49	$610.50	$610.50