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	$89.97	12.834%	$101.5167	$101.52	$101.50	$101.50
Purchase #2	$79.93	11.688%	$89.2722	$89.27	$89.25	$89.30
Purchase #3	$20.52	13.192%	$23.227	$23.23	$23.25	$23.20
Purchase #4	$173.50	11.298%	$193.102	$193.10	$193.10	$193.10
Purchase #5	$104.73	6.371%	$111.4023	$111.40	$111.40	$111.40
Purchase #6	$208.77	13.270%	$236.4738	$236.47	$236.45	$236.50
Purchase #7	$54.80	5.508%	$57.8184	$57.82	$57.80	$57.80
7 purchase totals =	$732.22		$812.8124	$812.81	$812.75	$812.80