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	$98.77	12.824%	$111.4363	$111.44	$111.45	$111.40
Purchase #2	$55.78	3.724%	$57.8572	$57.86	$57.85	$57.90
Purchase #3	$185.60	3.781%	$192.6175	$192.62	$192.60	$192.60
Purchase #4	$214.49	5.815%	$226.9626	$226.96	$226.95	$227.00
Purchase #5	$193.99	11.130%	$215.5811	$215.58	$215.60	$215.60
Purchase #6	$152.76	4.342%	$159.3928	$159.39	$159.40	$159.40
Purchase #7	$164.71	5.464%	$173.7098	$173.71	$173.70	$173.70
7 purchase totals =	$1,066.10		$1,137.5573	$1,137.56	$1,137.55	$1,137.60