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	$107.53	5.635%	$113.5893	$113.59	$113.60	$113.60
Purchase #2	$12.42	7.748%	$13.3823	$13.38	$13.40	$13.40
Purchase #3	$154.30	12.524%	$173.6245	$173.62	$173.60	$173.60
Purchase #4	$31.43	3.195%	$32.4342	$32.43	$32.45	$32.40
Purchase #5	$237.81	3.605%	$246.3831	$246.38	$246.40	$246.40
Purchase #6	$33.32	11.172%	$37.0425	$37.04	$37.05	$37.00
Purchase #7	$82.39	9.346%	$90.0902	$90.09	$90.10	$90.10
7 purchase totals =	$659.20		$706.5461	$706.53	$706.60	$706.50