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	$216.28	3.390%	$223.6119	$223.61	$223.60	$223.60
Purchase #2	$246.29	12.600%	$277.3225	$277.32	$277.30	$277.30
Purchase #3	$130.32	11.434%	$145.2208	$145.22	$145.20	$145.20
Purchase #4	$148.42	10.539%	$164.062	$164.06	$164.05	$164.10
Purchase #5	$186.34	3.278%	$192.4482	$192.45	$192.45	$192.40
Purchase #6	$36.99	8.613%	$40.1759	$40.18	$40.20	$40.20
Purchase #7	$174.32	4.699%	$182.5113	$182.51	$182.50	$182.50
7 purchase totals =	$1,138.96		$1,225.3526	$1,225.35	$1,225.30	$1,225.30