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	$65.50	3.190%	$67.5895	$67.59	$67.60	$67.60
Purchase #2	$26.25	12.571%	$29.5499	$29.55	$29.55	$29.50
Purchase #3	$102.39	9.246%	$111.857	$111.86	$111.85	$111.90
Purchase #4	$156.91	8.585%	$170.3807	$170.38	$170.40	$170.40
Purchase #5	$145.48	8.466%	$157.7963	$157.80	$157.80	$157.80
Purchase #6	$176.77	11.425%	$196.966	$196.97	$196.95	$197.00
Purchase #7	$234.79	12.661%	$264.5168	$264.52	$264.50	$264.50
7 purchase totals =	$908.09		$998.6562	$998.67	$998.65	$998.70