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	$197.62	9.790%	$216.967	$216.97	$216.95	$217.00
Purchase #2	$244.88	4.465%	$255.8139	$255.81	$255.80	$255.80
Purchase #3	$11.85	12.301%	$13.3077	$13.31	$13.30	$13.30
Purchase #4	$38.47	5.570%	$40.6128	$40.61	$40.60	$40.60
Purchase #5	$117.86	12.363%	$132.431	$132.43	$132.45	$132.40
Purchase #6	$146.51	13.403%	$166.1467	$166.15	$166.15	$166.10
Purchase #7	$35.60	7.519%	$38.2768	$38.28	$38.30	$38.30
7 purchase totals =	$792.79		$863.5559	$863.56	$863.55	$863.50