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	$148.33	13.372%	$168.1647	$168.16	$168.15	$168.20
Purchase #2	$12.25	3.700%	$12.7033	$12.70	$12.70	$12.70
Purchase #3	$22.42	9.721%	$24.5994	$24.60	$24.60	$24.60
Purchase #4	$105.59	6.582%	$112.5399	$112.54	$112.55	$112.50
Purchase #5	$59.73	3.858%	$62.0344	$62.03	$62.05	$62.00
Purchase #6	$11.35	8.211%	$12.2819	$12.28	$12.30	$12.30
Purchase #7	$136.56	4.734%	$143.0248	$143.02	$143.00	$143.00
7 purchase totals =	$496.23		$535.3484	$535.33	$535.35	$535.30