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	$63.61	4.577%	$66.5214	$66.52	$66.50	$66.50
Purchase #2	$60.68	8.670%	$65.941	$65.94	$65.95	$65.90
Purchase #3	$157.41	4.857%	$165.0554	$165.06	$165.05	$165.10
Purchase #4	$103.94	6.298%	$110.4861	$110.49	$110.50	$110.50
Purchase #5	$29.85	12.690%	$33.638	$33.64	$33.65	$33.60
Purchase #6	$88.27	6.427%	$93.9431	$93.94	$93.95	$93.90
Purchase #7	$103.88	10.239%	$114.5163	$114.52	$114.50	$114.50
7 purchase totals =	$607.64		$650.1013	$650.11	$650.10	$650.00