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	$80.69	7.345%	$86.6167	$86.62	$86.60	$86.60
Purchase #2	$29.35	10.236%	$32.3543	$32.35	$32.35	$32.40
Purchase #3	$160.89	7.563%	$173.0581	$173.06	$173.05	$173.10
Purchase #4	$50.73	10.719%	$56.1677	$56.17	$56.15	$56.20
Purchase #5	$18.34	8.380%	$19.8769	$19.88	$19.90	$19.90
Purchase #6	$219.58	8.610%	$238.4858	$238.49	$238.50	$238.50
Purchase #7	$119.58	10.239%	$131.8238	$131.82	$131.80	$131.80
7 purchase totals =	$679.16		$738.3833	$738.39	$738.35	$738.50