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	$43.46	7.325%	$46.6434	$46.64	$46.65	$46.60
Purchase #2	$101.39	11.372%	$112.9201	$112.92	$112.90	$112.90
Purchase #3	$71.44	4.726%	$74.8163	$74.82	$74.80	$74.80
Purchase #4	$139.40	5.390%	$146.9137	$146.91	$146.90	$146.90
Purchase #5	$135.69	12.593%	$152.7774	$152.78	$152.80	$152.80
Purchase #6	$132.60	4.772%	$138.9277	$138.93	$138.95	$138.90
Purchase #7	$101.85	3.211%	$105.1204	$105.12	$105.10	$105.10
7 purchase totals =	$725.83		$778.1190	$778.12	$778.10	$778.00