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	$144.99	5.572%	$153.0688	$153.07	$153.05	$153.10
Purchase #2	$43.78	4.827%	$45.8933	$45.89	$45.90	$45.90
Purchase #3	$232.37	4.447%	$242.7035	$242.70	$242.70	$242.70
Purchase #4	$247.89	3.603%	$256.8215	$256.82	$256.80	$256.80
Purchase #5	$57.59	3.434%	$59.5676	$59.57	$59.55	$59.60
Purchase #6	$241.56	4.482%	$252.3867	$252.39	$252.40	$252.40
Purchase #7	$54.85	8.541%	$59.5347	$59.53	$59.55	$59.50
7 purchase totals =	$1,023.03		$1,069.9761	$1,069.97	$1,069.95	$1,070.00