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	$108.57	3.772%	$112.6653	$112.67	$112.65	$112.70
Purchase #2	$157.78	3.166%	$162.7753	$162.78	$162.80	$162.80
Purchase #3	$18.58	11.393%	$20.6968	$20.70	$20.70	$20.70
Purchase #4	$41.32	4.104%	$43.0158	$43.02	$43.00	$43.00
Purchase #5	$80.32	11.795%	$89.7937	$89.79	$89.80	$89.80
Purchase #6	$138.27	13.686%	$157.1936	$157.19	$157.20	$157.20
Purchase #7	$147.81	9.798%	$162.2924	$162.29	$162.30	$162.30
7 purchase totals =	$692.65		$748.4329	$748.44	$748.45	$748.50