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	$45.52	6.786%	$48.609	$48.61	$48.60	$48.60
Purchase #2	$128.44	13.687%	$146.0196	$146.02	$146.00	$146.00
Purchase #3	$63.91	12.699%	$72.0259	$72.03	$72.05	$72.00
Purchase #4	$94.68	11.547%	$105.6127	$105.61	$105.60	$105.60
Purchase #5	$37.48	5.860%	$39.6763	$39.68	$39.70	$39.70
Purchase #6	$173.78	6.196%	$184.5474	$184.55	$184.55	$184.50
Purchase #7	$156.33	10.156%	$172.2069	$172.21	$172.20	$172.20
7 purchase totals =	$700.14		$768.6978	$768.71	$768.70	$768.60