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	$40.49	6.167%	$42.987	$42.99	$43.00	$43.00
Purchase #2	$54.57	9.385%	$59.6914	$59.69	$59.70	$59.70
Purchase #3	$242.49	7.365%	$260.3494	$260.35	$260.35	$260.30
Purchase #4	$220.86	5.843%	$233.7648	$233.76	$233.75	$233.80
Purchase #5	$156.85	10.687%	$173.6126	$173.61	$173.60	$173.60
Purchase #6	$184.68	3.133%	$190.466	$190.47	$190.45	$190.50
Purchase #7	$32.97	13.559%	$37.4404	$37.44	$37.45	$37.40
7 purchase totals =	$932.91		$998.3116	$998.31	$998.30	$998.30