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	$55.83	6.659%	$59.5477	$59.55	$59.55	$59.50
Purchase #2	$111.89	12.671%	$126.0676	$126.07	$126.05	$126.10
Purchase #3	$139.66	13.448%	$158.4415	$158.44	$158.45	$158.40
Purchase #4	$167.98	7.505%	$180.5869	$180.59	$180.60	$180.60
Purchase #5	$121.31	10.777%	$134.3836	$134.38	$134.40	$134.40
Purchase #6	$241.40	8.584%	$262.1218	$262.12	$262.10	$262.10
Purchase #7	$140.82	12.138%	$157.9127	$157.91	$157.90	$157.90
7 purchase totals =	$978.89		$1,079.0618	$1,079.06	$1,079.05	$1,079.00