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	$201.51	8.342%	$218.32	$218.32	$218.30	$218.30
Purchase #2	$208.38	7.747%	$224.5232	$224.52	$224.50	$224.50
Purchase #3	$64.82	3.670%	$67.1989	$67.20	$67.20	$67.20
Purchase #4	$233.45	3.443%	$241.4877	$241.49	$241.50	$241.50
Purchase #5	$228.93	11.271%	$254.7327	$254.73	$254.75	$254.70
Purchase #6	$18.57	10.518%	$20.5232	$20.52	$20.50	$20.50
Purchase #7	$185.93	6.660%	$198.3129	$198.31	$198.30	$198.30
7 purchase totals =	$1,141.59		$1,225.0986	$1,225.09	$1,225.05	$1,225.00