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	$192.89	13.341%	$218.6235	$218.62	$218.60	$218.60
Purchase #2	$130.76	6.371%	$139.0907	$139.09	$139.10	$139.10
Purchase #3	$227.31	12.239%	$255.1305	$255.13	$255.15	$255.10
Purchase #4	$117.58	4.774%	$123.1933	$123.19	$123.20	$123.20
Purchase #5	$227.64	3.722%	$236.1128	$236.11	$236.10	$236.10
Purchase #6	$33.85	11.103%	$37.6084	$37.61	$37.60	$37.60
Purchase #7	$46.91	3.538%	$48.5697	$48.57	$48.55	$48.60
7 purchase totals =	$976.94		$1,058.3289	$1,058.32	$1,058.30	$1,058.30