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	$112.95	12.647%	$127.2348	$127.23	$127.25	$127.20
Purchase #2	$81.38	11.152%	$90.4555	$90.46	$90.45	$90.50
Purchase #3	$106.31	5.773%	$112.4473	$112.45	$112.45	$112.40
Purchase #4	$105.49	10.593%	$116.6646	$116.66	$116.65	$116.70
Purchase #5	$126.85	12.597%	$142.8293	$142.83	$142.85	$142.80
Purchase #6	$157.36	4.247%	$164.0431	$164.04	$164.05	$164.00
Purchase #7	$138.36	7.555%	$148.8131	$148.81	$148.80	$148.80
7 purchase totals =	$828.70		$902.4877	$902.48	$902.50	$902.40