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	$237.53	6.250%	$252.3756	$252.38	$252.40	$252.40
Purchase #2	$11.85	8.381%	$12.8431	$12.84	$12.85	$12.80
Purchase #3	$116.38	6.457%	$123.8947	$123.89	$123.90	$123.90
Purchase #4	$18.67	7.794%	$20.1251	$20.13	$20.15	$20.10
Purchase #5	$203.59	8.363%	$220.6162	$220.62	$220.60	$220.60
Purchase #6	$220.47	13.321%	$249.8388	$249.84	$249.85	$249.80
Purchase #7	$81.42	10.302%	$89.8079	$89.81	$89.80	$89.80
7 purchase totals =	$889.91		$969.5014	$969.51	$969.55	$969.40