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	$200.48	10.874%	$222.2802	$222.28	$222.30	$222.30
Purchase #2	$95.91	7.483%	$103.0869	$103.09	$103.10	$103.10
Purchase #3	$17.31	7.401%	$18.5911	$18.59	$18.60	$18.60
Purchase #4	$40.51	6.383%	$43.0958	$43.10	$43.10	$43.10
Purchase #5	$203.49	13.813%	$231.5981	$231.60	$231.60	$231.60
Purchase #6	$243.45	11.687%	$271.902	$271.90	$271.90	$271.90
Purchase #7	$202.89	5.773%	$214.6028	$214.60	$214.60	$214.60
7 purchase totals =	$1,004.04		$1,105.1569	$1,105.16	$1,105.20	$1,105.20