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	$142.77	6.655%	$152.2713	$152.27	$152.25	$152.30
Purchase #2	$215.94	3.500%	$223.4979	$223.50	$223.50	$223.50
Purchase #3	$21.87	3.397%	$22.6129	$22.61	$22.60	$22.60
Purchase #4	$56.57	12.390%	$63.579	$63.58	$63.60	$63.60
Purchase #5	$56.96	13.343%	$64.5602	$64.56	$64.55	$64.60
Purchase #6	$143.74	10.509%	$158.8456	$158.85	$158.85	$158.80
Purchase #7	$47.79	4.423%	$49.9038	$49.90	$49.90	$49.90
7 purchase totals =	$685.64		$735.2707	$735.27	$735.25	$735.30