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	$40.63	11.287%	$45.2159	$45.22	$45.20	$45.20
Purchase #2	$146.82	4.553%	$153.5047	$153.50	$153.50	$153.50
Purchase #3	$183.84	3.627%	$190.5079	$190.51	$190.50	$190.50
Purchase #4	$124.83	4.754%	$130.7644	$130.76	$130.75	$130.80
Purchase #5	$31.64	3.840%	$32.855	$32.86	$32.85	$32.90
Purchase #6	$167.34	12.549%	$188.3395	$188.34	$188.35	$188.30
Purchase #7	$128.26	10.401%	$141.6003	$141.60	$141.60	$141.60
7 purchase totals =	$823.36		$882.7877	$882.79	$882.75	$882.80