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	$40.99	8.168%	$44.3381	$44.34	$44.35	$44.30
Purchase #2	$90.79	10.657%	$100.4655	$100.47	$100.45	$100.50
Purchase #3	$139.90	5.441%	$147.512	$147.51	$147.50	$147.50
Purchase #4	$233.27	13.231%	$264.134	$264.13	$264.15	$264.10
Purchase #5	$14.66	7.110%	$15.7023	$15.70	$15.70	$15.70
Purchase #6	$235.41	12.789%	$265.5166	$265.52	$265.50	$265.50
Purchase #7	$69.85	3.802%	$72.5057	$72.51	$72.50	$72.50
7 purchase totals =	$824.87		$910.1742	$910.18	$910.15	$910.10