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	$82.99	6.242%	$88.1702	$88.17	$88.15	$88.20
Purchase #2	$205.29	4.314%	$214.1462	$214.15	$214.15	$214.10
Purchase #3	$137.69	10.600%	$152.2851	$152.29	$152.30	$152.30
Purchase #4	$186.39	6.452%	$198.4159	$198.42	$198.40	$198.40
Purchase #5	$15.80	13.771%	$17.9758	$17.98	$18.00	$18.00
Purchase #6	$144.25	4.562%	$150.8307	$150.83	$150.85	$150.80
Purchase #7	$38.89	4.845%	$40.7742	$40.77	$40.75	$40.80
7 purchase totals =	$811.30		$862.5981	$862.61	$862.60	$862.60