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	$55.98	10.252%	$61.7191	$61.72	$61.70	$61.70
Purchase #2	$166.58	6.808%	$177.9208	$177.92	$177.90	$177.90
Purchase #3	$99.56	6.164%	$105.6969	$105.70	$105.70	$105.70
Purchase #4	$143.53	13.292%	$162.608	$162.61	$162.60	$162.60
Purchase #5	$24.69	4.675%	$25.8443	$25.84	$25.85	$25.80
Purchase #6	$134.28	10.861%	$148.8642	$148.86	$148.85	$148.90
Purchase #7	$119.60	3.396%	$123.6616	$123.66	$123.65	$123.70
7 purchase totals =	$744.22		$806.3149	$806.31	$806.25	$806.30