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	$214.61	12.442%	$241.3118	$241.31	$241.30	$241.30
Purchase #2	$108.29	10.443%	$119.5987	$119.60	$119.60	$119.60
Purchase #3	$181.65	7.840%	$195.8914	$195.89	$195.90	$195.90
Purchase #4	$124.85	5.579%	$131.8154	$131.82	$131.80	$131.80
Purchase #5	$12.41	4.798%	$13.0054	$13.01	$13.00	$13.00
Purchase #6	$13.72	11.105%	$15.2436	$15.24	$15.25	$15.20
Purchase #7	$46.94	6.544%	$50.0118	$50.01	$50.00	$50.00
7 purchase totals =	$702.47		$766.8781	$766.88	$766.85	$766.80