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	$11.35	10.341%	$12.5237	$12.52	$12.50	$12.50
Purchase #2	$132.62	5.498%	$139.9114	$139.91	$139.90	$139.90
Purchase #3	$73.45	7.446%	$78.9191	$78.92	$78.90	$78.90
Purchase #4	$24.81	13.477%	$28.1536	$28.15	$28.15	$28.20
Purchase #5	$16.96	4.757%	$17.7668	$17.77	$17.75	$17.80
Purchase #6	$37.75	3.698%	$39.146	$39.15	$39.15	$39.10
Purchase #7	$144.96	5.240%	$152.5559	$152.56	$152.55	$152.60
7 purchase totals =	$441.90		$468.9765	$468.98	$468.90	$469.00