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	$56.75	12.512%	$63.8506	$63.85	$63.85	$63.90
Purchase #2	$164.87	10.773%	$182.6314	$182.63	$182.65	$182.60
Purchase #3	$170.39	11.864%	$190.6051	$190.61	$190.60	$190.60
Purchase #4	$91.78	13.249%	$103.9399	$103.94	$103.95	$103.90
Purchase #5	$139.86	3.526%	$144.7915	$144.79	$144.80	$144.80
Purchase #6	$250.92	11.303%	$279.2815	$279.28	$279.30	$279.30
Purchase #7	$96.67	3.178%	$99.7422	$99.74	$99.75	$99.70
7 purchase totals =	$971.24		$1,064.8422	$1,064.84	$1,064.90	$1,064.80