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	$188.29	12.351%	$211.5457	$211.55	$211.55	$211.50
Purchase #2	$127.83	3.255%	$131.9909	$131.99	$132.00	$132.00
Purchase #3	$9.52	5.700%	$10.0626	$10.06	$10.05	$10.10
Purchase #4	$56.97	4.596%	$59.5883	$59.59	$59.60	$59.60
Purchase #5	$54.34	13.157%	$61.4895	$61.49	$61.50	$61.50
Purchase #6	$139.30	13.141%	$157.6054	$157.61	$157.60	$157.60
Purchase #7	$35.62	12.189%	$39.9617	$39.96	$39.95	$40.00
7 purchase totals =	$611.87		$672.2441	$672.25	$672.25	$672.30