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	$73.43	4.611%	$76.8159	$76.82	$76.80	$76.80
Purchase #2	$30.40	7.367%	$32.6396	$32.64	$32.65	$32.60
Purchase #3	$112.82	9.618%	$123.671	$123.67	$123.65	$123.70
Purchase #4	$44.32	13.388%	$50.2536	$50.25	$50.25	$50.30
Purchase #5	$173.95	10.648%	$192.4722	$192.47	$192.45	$192.50
Purchase #6	$170.47	7.689%	$183.5774	$183.58	$183.60	$183.60
Purchase #7	$73.96	4.278%	$77.124	$77.12	$77.10	$77.10
7 purchase totals =	$679.35		$736.5537	$736.55	$736.50	$736.60