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	$64.57	10.611%	$71.4215	$71.42	$71.40	$71.40
Purchase #2	$43.90	3.803%	$45.5695	$45.57	$45.55	$45.60
Purchase #3	$32.66	3.611%	$33.8394	$33.84	$33.85	$33.80
Purchase #4	$82.61	9.726%	$90.6446	$90.64	$90.65	$90.60
Purchase #5	$151.73	6.390%	$161.4255	$161.43	$161.45	$161.40
Purchase #6	$192.60	9.231%	$210.3789	$210.38	$210.40	$210.40
Purchase #7	$103.30	13.806%	$117.5616	$117.56	$117.55	$117.60
7 purchase totals =	$671.37		$730.8410	$730.84	$730.85	$730.80