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	$181.78	5.640%	$192.0324	$192.03	$192.05	$192.00
Purchase #2	$236.85	7.390%	$254.3532	$254.35	$254.35	$254.40
Purchase #3	$153.40	10.779%	$169.935	$169.94	$169.95	$169.90
Purchase #4	$24.32	12.537%	$27.369	$27.37	$27.35	$27.40
Purchase #5	$118.98	11.183%	$132.2855	$132.29	$132.30	$132.30
Purchase #6	$121.60	4.670%	$127.2787	$127.28	$127.30	$127.30
Purchase #7	$91.92	13.738%	$104.548	$104.55	$104.55	$104.50
7 purchase totals =	$928.85		$1,007.8018	$1,007.81	$1,007.85	$1,007.80