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	$182.71	13.223%	$206.8697	$206.87	$206.85	$206.90
Purchase #2	$70.90	11.189%	$78.833	$78.83	$78.85	$78.80
Purchase #3	$209.98	7.104%	$224.897	$224.90	$224.90	$224.90
Purchase #4	$40.72	9.714%	$44.6755	$44.68	$44.70	$44.70
Purchase #5	$248.86	9.524%	$272.5614	$272.56	$272.55	$272.60
Purchase #6	$149.87	11.176%	$166.6195	$166.62	$166.60	$166.60
Purchase #7	$130.57	11.681%	$145.8219	$145.82	$145.80	$145.80
7 purchase totals =	$1,033.61		$1,140.2780	$1,140.28	$1,140.25	$1,140.30