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	$153.58	8.629%	$166.8324	$166.83	$166.85	$166.80
Purchase #2	$24.83	7.225%	$26.624	$26.62	$26.60	$26.60
Purchase #3	$138.75	5.812%	$146.8142	$146.81	$146.80	$146.80
Purchase #4	$190.81	3.165%	$196.8491	$196.85	$196.85	$196.80
Purchase #5	$249.52	3.222%	$257.5595	$257.56	$257.55	$257.60
Purchase #6	$183.60	3.661%	$190.3216	$190.32	$190.30	$190.30
Purchase #7	$78.74	4.452%	$82.2455	$82.25	$82.25	$82.20
7 purchase totals =	$1,019.83		$1,067.2463	$1,067.24	$1,067.20	$1,067.10