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	$78.31	10.206%	$86.3023	$86.30	$86.30	$86.30
Purchase #2	$241.57	12.793%	$272.4741	$272.47	$272.45	$272.50
Purchase #3	$245.25	9.717%	$269.0809	$269.08	$269.10	$269.10
Purchase #4	$119.37	6.246%	$126.8259	$126.83	$126.85	$126.80
Purchase #5	$108.48	4.741%	$113.623	$113.62	$113.60	$113.60
Purchase #6	$24.31	12.168%	$27.268	$27.27	$27.25	$27.30
Purchase #7	$216.72	11.126%	$240.8323	$240.83	$240.85	$240.80
7 purchase totals =	$1,034.01		$1,136.4065	$1,136.40	$1,136.40	$1,136.40