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	$65.56	10.873%	$72.6883	$72.69	$72.70	$72.70
Purchase #2	$166.49	10.679%	$184.2695	$184.27	$184.25	$184.30
Purchase #3	$102.81	6.585%	$109.58	$109.58	$109.60	$109.60
Purchase #4	$227.58	3.554%	$235.6682	$235.67	$235.65	$235.70
Purchase #5	$69.71	9.523%	$76.3485	$76.35	$76.35	$76.30
Purchase #6	$31.68	3.225%	$32.7017	$32.70	$32.70	$32.70
Purchase #7	$93.89	11.726%	$104.8995	$104.90	$104.90	$104.90
7 purchase totals =	$757.72		$816.1557	$816.16	$816.15	$816.20