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	$176.96	12.649%	$199.3437	$199.34	$199.35	$199.30
Purchase #2	$37.94	5.291%	$39.9474	$39.95	$39.95	$39.90
Purchase #3	$49.75	10.197%	$54.823	$54.82	$54.80	$54.80
Purchase #4	$63.41	7.157%	$67.9483	$67.95	$67.95	$67.90
Purchase #5	$153.27	4.707%	$160.4844	$160.48	$160.50	$160.50
Purchase #6	$60.53	11.613%	$67.5593	$67.56	$67.55	$67.60
Purchase #7	$91.90	8.178%	$99.4156	$99.42	$99.40	$99.40
7 purchase totals =	$633.76		$689.5217	$689.52	$689.50	$689.40