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	$214.30	3.869%	$222.5913	$222.59	$222.60	$222.60
Purchase #2	$91.68	13.546%	$104.099	$104.10	$104.10	$104.10
Purchase #3	$93.81	11.869%	$104.9443	$104.94	$104.95	$104.90
Purchase #4	$95.93	13.112%	$108.5083	$108.51	$108.50	$108.50
Purchase #5	$34.55	5.622%	$36.4924	$36.49	$36.50	$36.50
Purchase #6	$162.79	3.522%	$168.5235	$168.52	$168.50	$168.50
Purchase #7	$15.61	11.847%	$17.4593	$17.46	$17.45	$17.50
7 purchase totals =	$708.67		$762.6181	$762.61	$762.60	$762.60