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	$95.43	4.769%	$99.9811	$99.98	$100.00	$100.00
Purchase #2	$12.29	4.617%	$12.8574	$12.86	$12.85	$12.90
Purchase #3	$142.99	6.386%	$152.1213	$152.12	$152.10	$152.10
Purchase #4	$20.48	5.372%	$21.5802	$21.58	$21.60	$21.60
Purchase #5	$26.40	5.423%	$27.8317	$27.83	$27.85	$27.80
Purchase #6	$46.62	5.364%	$49.1207	$49.12	$49.10	$49.10
Purchase #7	$142.52	6.503%	$151.7881	$151.79	$151.80	$151.80
7 purchase totals =	$486.73		$515.2805	$515.28	$515.30	$515.30