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	$156.42	10.710%	$173.1726	$173.17	$173.15	$173.20
Purchase #2	$30.50	12.692%	$34.3711	$34.37	$34.35	$34.40
Purchase #3	$217.82	12.602%	$245.2697	$245.27	$245.25	$245.30
Purchase #4	$45.79	6.632%	$48.8268	$48.83	$48.85	$48.80
Purchase #5	$42.62	7.667%	$45.8877	$45.89	$45.90	$45.90
Purchase #6	$75.82	7.244%	$81.3124	$81.31	$81.30	$81.30
Purchase #7	$94.62	7.109%	$101.3465	$101.35	$101.35	$101.30
7 purchase totals =	$663.59		$730.1868	$730.19	$730.15	$730.20