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	$13.37	6.570%	$14.2484	$14.25	$14.25	$14.20
Purchase #2	$185.45	7.234%	$198.8655	$198.87	$198.85	$198.90
Purchase #3	$157.68	13.483%	$178.94	$178.94	$178.95	$178.90
Purchase #4	$70.59	11.827%	$78.9387	$78.94	$78.95	$78.90
Purchase #5	$189.59	13.439%	$215.069	$215.07	$215.05	$215.10
Purchase #6	$57.59	3.485%	$59.597	$59.60	$59.60	$59.60
Purchase #7	$216.57	10.103%	$238.4501	$238.45	$238.45	$238.50
7 purchase totals =	$890.84		$984.1087	$984.12	$984.10	$984.10