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	$143.43	4.638%	$150.0823	$150.08	$150.10	$150.10
Purchase #2	$133.64	3.167%	$137.8724	$137.87	$137.85	$137.90
Purchase #3	$85.76	5.761%	$90.7006	$90.70	$90.70	$90.70
Purchase #4	$172.72	7.201%	$185.1576	$185.16	$185.15	$185.20
Purchase #5	$226.28	9.799%	$248.4532	$248.45	$248.45	$248.50
Purchase #6	$66.41	12.498%	$74.7099	$74.71	$74.70	$74.70
Purchase #7	$160.29	7.684%	$172.6067	$172.61	$172.60	$172.60
7 purchase totals =	$988.53		$1,059.5827	$1,059.58	$1,059.55	$1,059.70