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	$41.34	10.859%	$45.8291	$45.83	$45.85	$45.80
Purchase #2	$130.61	11.393%	$145.4904	$145.49	$145.50	$145.50
Purchase #3	$50.34	13.840%	$57.3071	$57.31	$57.30	$57.30
Purchase #4	$230.60	11.476%	$257.0637	$257.06	$257.05	$257.10
Purchase #5	$120.36	5.531%	$127.0171	$127.02	$127.00	$127.00
Purchase #6	$220.82	4.715%	$231.2317	$231.23	$231.25	$231.20
Purchase #7	$151.43	7.496%	$162.7812	$162.78	$162.80	$162.80
7 purchase totals =	$945.50		$1,026.7203	$1,026.72	$1,026.75	$1,026.70