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	$148.34	9.616%	$162.6044	$162.60	$162.60	$162.60
Purchase #2	$200.33	13.635%	$227.645	$227.65	$227.65	$227.60
Purchase #3	$78.93	3.312%	$81.5442	$81.54	$81.55	$81.50
Purchase #4	$141.90	12.460%	$159.5807	$159.58	$159.60	$159.60
Purchase #5	$174.69	6.396%	$185.8632	$185.86	$185.85	$185.90
Purchase #6	$78.77	3.207%	$81.2962	$81.30	$81.30	$81.30
Purchase #7	$226.32	11.752%	$252.9171	$252.92	$252.90	$252.90
7 purchase totals =	$1,049.28		$1,151.4508	$1,151.45	$1,151.45	$1,151.40