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	$157.25	6.130%	$166.8894	$166.89	$166.90	$166.90
Purchase #2	$242.27	5.372%	$255.2847	$255.28	$255.30	$255.30
Purchase #3	$135.52	13.156%	$153.349	$153.35	$153.35	$153.30
Purchase #4	$89.65	13.125%	$101.4166	$101.42	$101.40	$101.40
Purchase #5	$42.66	5.543%	$45.0246	$45.02	$45.00	$45.00
Purchase #6	$204.79	8.569%	$222.3385	$222.34	$222.35	$222.30
Purchase #7	$17.59	9.614%	$19.2811	$19.28	$19.30	$19.30
7 purchase totals =	$889.73		$963.5839	$963.58	$963.60	$963.50