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	$222.48	8.414%	$241.1995	$241.20	$241.20	$241.20
Purchase #2	$105.49	5.776%	$111.5831	$111.58	$111.60	$111.60
Purchase #3	$158.94	13.552%	$180.4795	$180.48	$180.50	$180.50
Purchase #4	$97.89	4.751%	$102.5408	$102.54	$102.55	$102.50
Purchase #5	$124.39	3.455%	$128.6877	$128.69	$128.70	$128.70
Purchase #6	$216.26	8.756%	$235.1957	$235.20	$235.20	$235.20
Purchase #7	$13.27	9.758%	$14.5649	$14.56	$14.55	$14.60
7 purchase totals =	$938.72		$1,014.2512	$1,014.25	$1,014.30	$1,014.30