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	$95.77	9.461%	$104.8308	$104.83	$104.85	$104.80
Purchase #2	$58.92	11.396%	$65.6345	$65.63	$65.65	$65.60
Purchase #3	$16.52	6.498%	$17.5935	$17.59	$17.60	$17.60
Purchase #4	$145.94	7.150%	$156.3747	$156.37	$156.35	$156.40
Purchase #5	$218.56	6.414%	$232.5784	$232.58	$232.60	$232.60
Purchase #6	$81.88	10.239%	$90.2637	$90.26	$90.25	$90.30
Purchase #7	$70.65	10.506%	$78.0725	$78.07	$78.05	$78.10
7 purchase totals =	$688.24		$745.3481	$745.33	$745.35	$745.40