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	$41.79	3.720%	$43.3446	$43.34	$43.35	$43.30
Purchase #2	$5.98	6.706%	$6.381	$6.38	$6.40	$6.40
Purchase #3	$56.95	4.255%	$59.3732	$59.37	$59.35	$59.40
Purchase #4	$53.41	6.848%	$57.0675	$57.07	$57.05	$57.10
Purchase #5	$9.60	9.709%	$10.5321	$10.53	$10.55	$10.50
Purchase #6	$202.66	5.864%	$214.544	$214.54	$214.55	$214.50
Purchase #7	$173.56	13.408%	$196.8309	$196.83	$196.85	$196.80
7 purchase totals =	$543.95		$588.0733	$588.06	$588.10	$588.00