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	$138.52	9.670%	$151.9149	$151.91	$151.90	$151.90
Purchase #2	$85.46	8.317%	$92.5677	$92.57	$92.55	$92.60
Purchase #3	$234.59	5.227%	$246.852	$246.85	$246.85	$246.90
Purchase #4	$216.98	12.737%	$244.6167	$244.62	$244.60	$244.60
Purchase #5	$116.36	8.714%	$126.4996	$126.50	$126.50	$126.50
Purchase #6	$130.85	10.496%	$144.584	$144.58	$144.60	$144.60
Purchase #7	$79.64	10.855%	$88.2849	$88.28	$88.30	$88.30
7 purchase totals =	$1,002.40		$1,095.3198	$1,095.31	$1,095.30	$1,095.40