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	$106.60	4.614%	$111.5185	$111.52	$111.50	$111.50
Purchase #2	$151.89	13.353%	$172.1719	$172.17	$172.15	$172.20
Purchase #3	$194.61	12.868%	$219.6524	$219.65	$219.65	$219.70
Purchase #4	$226.27	7.406%	$243.0276	$243.03	$243.05	$243.00
Purchase #5	$24.57	3.380%	$25.4005	$25.40	$25.40	$25.40
Purchase #6	$12.66	7.176%	$13.5685	$13.57	$13.55	$13.60
Purchase #7	$74.84	6.685%	$79.8431	$79.84	$79.85	$79.80
7 purchase totals =	$791.44		$865.1825	$865.18	$865.15	$865.20