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	$185.46	9.248%	$202.6113	$202.61	$202.60	$202.60
Purchase #2	$47.91	9.753%	$52.5827	$52.58	$52.60	$52.60
Purchase #3	$152.85	8.668%	$166.099	$166.10	$166.10	$166.10
Purchase #4	$68.97	4.758%	$72.2516	$72.25	$72.25	$72.30
Purchase #5	$50.83	9.275%	$55.5445	$55.54	$55.55	$55.50
Purchase #6	$129.99	12.605%	$146.3752	$146.38	$146.40	$146.40
Purchase #7	$29.80	7.106%	$31.9176	$31.92	$31.90	$31.90
7 purchase totals =	$665.81		$727.3819	$727.38	$727.40	$727.40