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	$87.79	3.575%	$90.9285	$90.93	$90.95	$90.90
Purchase #2	$65.28	10.709%	$72.2708	$72.27	$72.25	$72.30
Purchase #3	$135.28	11.635%	$151.0198	$151.02	$151.00	$151.00
Purchase #4	$41.89	11.705%	$46.7932	$46.79	$46.80	$46.80
Purchase #5	$182.42	10.517%	$201.6051	$201.61	$201.60	$201.60
Purchase #6	$117.83	5.636%	$124.4709	$124.47	$124.45	$124.50
Purchase #7	$26.84	3.534%	$27.7885	$27.79	$27.80	$27.80
7 purchase totals =	$657.33		$714.8768	$714.88	$714.85	$714.90