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	$40.91	5.458%	$43.1429	$43.14	$43.15	$43.10
Purchase #2	$86.71	4.228%	$90.3761	$90.38	$90.40	$90.40
Purchase #3	$101.33	10.340%	$111.8075	$111.81	$111.80	$111.80
Purchase #4	$162.68	6.424%	$173.1306	$173.13	$173.15	$173.10
Purchase #5	$100.53	13.493%	$114.0945	$114.09	$114.10	$114.10
Purchase #6	$221.95	6.839%	$237.1292	$237.13	$237.15	$237.10
Purchase #7	$19.95	4.527%	$20.8531	$20.85	$20.85	$20.90
7 purchase totals =	$734.06		$790.5339	$790.53	$790.60	$790.50