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	$171.67	12.608%	$193.3142	$193.31	$193.30	$193.30
Purchase #2	$13.66	12.802%	$15.4088	$15.41	$15.40	$15.40
Purchase #3	$21.98	3.855%	$22.8273	$22.83	$22.85	$22.80
Purchase #4	$74.81	4.810%	$78.4084	$78.41	$78.40	$78.40
Purchase #5	$205.49	13.778%	$233.8024	$233.80	$233.80	$233.80
Purchase #6	$189.84	4.391%	$198.1759	$198.18	$198.20	$198.20
Purchase #7	$137.40	4.724%	$143.8908	$143.89	$143.90	$143.90
7 purchase totals =	$814.85		$885.8278	$885.83	$885.85	$885.80