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	$133.73	5.722%	$141.382	$141.38	$141.40	$141.40
Purchase #2	$249.32	10.324%	$275.0598	$275.06	$275.05	$275.10
Purchase #3	$39.76	13.282%	$45.0409	$45.04	$45.05	$45.00
Purchase #4	$140.68	11.850%	$157.3506	$157.35	$157.35	$157.40
Purchase #5	$84.67	11.587%	$94.4807	$94.48	$94.50	$94.50
Purchase #6	$184.38	3.420%	$190.6858	$190.69	$190.70	$190.70
Purchase #7	$56.99	4.540%	$59.5773	$59.58	$59.60	$59.60
7 purchase totals =	$889.53		$963.5771	$963.58	$963.65	$963.70