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	$183.34	4.825%	$192.1862	$192.19	$192.20	$192.20
Purchase #2	$116.37	4.743%	$121.8894	$121.89	$121.90	$121.90
Purchase #3	$62.69	5.870%	$66.3699	$66.37	$66.35	$66.40
Purchase #4	$11.28	6.396%	$12.0015	$12.00	$12.00	$12.00
Purchase #5	$96.82	3.603%	$100.3084	$100.31	$100.30	$100.30
Purchase #6	$126.56	13.321%	$143.4191	$143.42	$143.40	$143.40
Purchase #7	$150.89	3.297%	$155.8648	$155.86	$155.85	$155.90
7 purchase totals =	$747.95		$792.0393	$792.04	$792.00	$792.10