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	$60.42	7.679%	$65.0597	$65.06	$65.05	$65.10
Purchase #2	$60.45	11.412%	$67.3486	$67.35	$67.35	$67.30
Purchase #3	$198.98	4.773%	$208.4773	$208.48	$208.50	$208.50
Purchase #4	$119.32	5.633%	$126.0413	$126.04	$126.05	$126.00
Purchase #5	$52.89	9.120%	$57.7136	$57.71	$57.70	$57.70
Purchase #6	$76.30	7.833%	$82.2766	$82.28	$82.30	$82.30
Purchase #7	$145.62	13.810%	$165.7301	$165.73	$165.75	$165.70
7 purchase totals =	$713.98		$772.6472	$772.65	$772.70	$772.60