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	$103.55	11.761%	$115.7285	$115.73	$115.75	$115.70
Purchase #2	$14.38	4.138%	$14.975	$14.98	$15.00	$15.00
Purchase #3	$64.63	11.614%	$72.1361	$72.14	$72.15	$72.10
Purchase #4	$63.96	13.603%	$72.6605	$72.66	$72.65	$72.70
Purchase #5	$178.81	12.113%	$200.4693	$200.47	$200.45	$200.50
Purchase #6	$164.67	6.604%	$175.5448	$175.54	$175.55	$175.50
Purchase #7	$230.67	7.540%	$248.0625	$248.06	$248.05	$248.10
7 purchase totals =	$820.67		$899.5767	$899.58	$899.60	$899.60