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	$198.72	4.714%	$208.0877	$208.09	$208.10	$208.10
Purchase #2	$37.45	8.523%	$40.6419	$40.64	$40.65	$40.60
Purchase #3	$162.77	12.469%	$183.0658	$183.07	$183.05	$183.10
Purchase #4	$220.56	5.302%	$232.2541	$232.25	$232.25	$232.30
Purchase #5	$166.31	11.758%	$185.8647	$185.86	$185.85	$185.90
Purchase #6	$32.39	9.730%	$35.5415	$35.54	$35.55	$35.50
Purchase #7	$171.74	8.378%	$186.1284	$186.13	$186.15	$186.10
7 purchase totals =	$989.94		$1,071.5841	$1,071.58	$1,071.60	$1,071.60