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	$178.32	7.617%	$191.9026	$191.90	$191.90	$191.90
Purchase #2	$33.51	12.314%	$37.6364	$37.64	$37.65	$37.60
Purchase #3	$192.60	12.236%	$216.1665	$216.17	$216.15	$216.20
Purchase #4	$44.51	13.580%	$50.5545	$50.55	$50.55	$50.60
Purchase #5	$31.92	8.194%	$34.5355	$34.54	$34.55	$34.50
Purchase #6	$135.88	5.493%	$143.3439	$143.34	$143.35	$143.30
Purchase #7	$169.38	7.636%	$182.3139	$182.31	$182.30	$182.30
7 purchase totals =	$786.12		$856.4533	$856.45	$856.45	$856.40