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	$55.86	12.794%	$63.0067	$63.01	$63.00	$63.00
Purchase #2	$35.46	4.376%	$37.0117	$37.01	$37.00	$37.00
Purchase #3	$79.25	4.447%	$82.7742	$82.77	$82.75	$82.80
Purchase #4	$177.94	11.213%	$197.8924	$197.89	$197.90	$197.90
Purchase #5	$153.46	13.218%	$173.7443	$173.74	$173.75	$173.70
Purchase #6	$67.49	4.365%	$70.4359	$70.44	$70.45	$70.40
Purchase #7	$111.33	7.486%	$119.6642	$119.66	$119.65	$119.70
7 purchase totals =	$680.79		$744.5294	$744.52	$744.50	$744.50