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	$157.84	8.509%	$171.2706	$171.27	$171.25	$171.30
Purchase #2	$141.79	7.652%	$152.6398	$152.64	$152.65	$152.60
Purchase #3	$167.58	13.472%	$190.1564	$190.16	$190.15	$190.20
Purchase #4	$89.50	6.495%	$95.313	$95.31	$95.30	$95.30
Purchase #5	$52.79	13.767%	$60.0576	$60.06	$60.05	$60.10
Purchase #6	$7.78	4.233%	$8.1093	$8.11	$8.10	$8.10
Purchase #7	$29.85	12.534%	$33.5914	$33.59	$33.60	$33.60
7 purchase totals =	$647.13		$711.1381	$711.14	$711.10	$711.20