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	$158.60	8.588%	$172.2206	$172.22	$172.20	$172.20
Purchase #2	$96.85	3.441%	$100.1826	$100.18	$100.20	$100.20
Purchase #3	$12.92	8.598%	$14.0309	$14.03	$14.05	$14.00
Purchase #4	$212.34	7.801%	$228.9046	$228.90	$228.90	$228.90
Purchase #5	$20.63	9.259%	$22.5401	$22.54	$22.55	$22.50
Purchase #6	$150.51	12.137%	$168.7774	$168.78	$168.80	$168.80
Purchase #7	$142.72	11.341%	$158.9059	$158.91	$158.90	$158.90
7 purchase totals =	$794.57		$865.5621	$865.56	$865.60	$865.50