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	$158.82	8.670%	$172.5897	$172.59	$172.60	$172.60
Purchase #2	$37.81	9.591%	$41.4364	$41.44	$41.45	$41.40
Purchase #3	$51.42	12.385%	$57.7884	$57.79	$57.80	$57.80
Purchase #4	$40.79	12.461%	$45.8728	$45.87	$45.85	$45.90
Purchase #5	$63.79	6.756%	$68.0997	$68.10	$68.10	$68.10
Purchase #6	$32.85	3.280%	$33.9275	$33.93	$33.95	$33.90
Purchase #7	$14.28	11.307%	$15.8946	$15.89	$15.90	$15.90
7 purchase totals =	$399.76		$435.6091	$435.61	$435.65	$435.60