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	$218.56	11.584%	$243.878	$243.88	$243.90	$243.90
Purchase #2	$28.50	7.504%	$30.6386	$30.64	$30.65	$30.60
Purchase #3	$164.67	6.554%	$175.4625	$175.46	$175.45	$175.50
Purchase #4	$35.59	5.608%	$37.5859	$37.59	$37.60	$37.60
Purchase #5	$53.49	9.395%	$58.5154	$58.52	$58.50	$58.50
Purchase #6	$205.85	10.695%	$227.8657	$227.87	$227.85	$227.90
Purchase #7	$124.72	12.176%	$139.9059	$139.91	$139.90	$139.90
7 purchase totals =	$831.38		$913.8520	$913.87	$913.85	$913.90