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	$172.81	13.808%	$196.6716	$196.67	$196.65	$196.70
Purchase #2	$238.36	12.273%	$267.6139	$267.61	$267.60	$267.60
Purchase #3	$93.65	13.231%	$106.0408	$106.04	$106.05	$106.00
Purchase #4	$29.93	8.703%	$32.5348	$32.53	$32.55	$32.50
Purchase #5	$134.82	12.206%	$151.2761	$151.28	$151.30	$151.30
Purchase #6	$238.69	4.799%	$250.1447	$250.14	$250.15	$250.10
Purchase #7	$35.26	9.708%	$38.683	$38.68	$38.70	$38.70
7 purchase totals =	$943.52		$1,042.9649	$1,042.95	$1,043.00	$1,042.90