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	$122.28	4.368%	$127.6212	$127.62	$127.60	$127.60
Purchase #2	$68.77	5.841%	$72.7869	$72.79	$72.80	$72.80
Purchase #3	$13.66	13.350%	$15.4836	$15.48	$15.50	$15.50
Purchase #4	$66.38	5.793%	$70.2254	$70.23	$70.25	$70.20
Purchase #5	$144.95	5.863%	$153.4484	$153.45	$153.45	$153.40
Purchase #6	$90.82	6.836%	$97.0285	$97.03	$97.05	$97.00
Purchase #7	$13.57	13.575%	$15.4121	$15.41	$15.40	$15.40
7 purchase totals =	$520.43		$552.0061	$552.01	$552.05	$551.90