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	$92.90	9.587%	$101.8063	$101.81	$101.80	$101.80
Purchase #2	$152.87	13.605%	$173.668	$173.67	$173.65	$173.70
Purchase #3	$31.84	10.733%	$35.2574	$35.26	$35.25	$35.30
Purchase #4	$40.95	12.812%	$46.1965	$46.20	$46.20	$46.20
Purchase #5	$216.99	9.737%	$238.1183	$238.12	$238.10	$238.10
Purchase #6	$181.60	3.760%	$188.4282	$188.43	$188.45	$188.40
Purchase #7	$82.54	9.517%	$90.3953	$90.40	$90.40	$90.40
7 purchase totals =	$799.69		$873.8700	$873.89	$873.85	$873.90