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	$101.79	3.835%	$105.6936	$105.69	$105.70	$105.70
Purchase #2	$65.99	4.468%	$68.9384	$68.94	$68.95	$68.90
Purchase #3	$104.68	13.680%	$119.0002	$119.00	$119.00	$119.00
Purchase #4	$50.40	8.131%	$54.498	$54.50	$54.50	$54.50
Purchase #5	$42.72	5.323%	$44.994	$44.99	$45.00	$45.00
Purchase #6	$173.83	9.386%	$190.1457	$190.15	$190.15	$190.10
Purchase #7	$134.32	3.109%	$138.496	$138.50	$138.50	$138.50
7 purchase totals =	$673.73		$721.7659	$721.77	$721.80	$721.70