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	$105.89	5.203%	$111.3995	$111.40	$111.40	$111.40
Purchase #2	$60.81	8.822%	$66.1747	$66.17	$66.15	$66.20
Purchase #3	$52.30	7.475%	$56.2094	$56.21	$56.20	$56.20
Purchase #4	$76.27	4.242%	$79.5054	$79.51	$79.50	$79.50
Purchase #5	$123.55	11.172%	$137.353	$137.35	$137.35	$137.40
Purchase #6	$108.43	3.248%	$111.9518	$111.95	$111.95	$112.00
Purchase #7	$159.32	8.194%	$172.3747	$172.37	$172.35	$172.40
7 purchase totals =	$686.57		$734.9685	$734.96	$734.90	$735.10