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	$170.32	5.401%	$179.519	$179.52	$179.50	$179.50
Purchase #2	$58.61	13.146%	$66.3149	$66.31	$66.30	$66.30
Purchase #3	$234.77	5.759%	$248.2904	$248.29	$248.30	$248.30
Purchase #4	$243.51	12.193%	$273.2012	$273.20	$273.20	$273.20
Purchase #5	$23.95	4.724%	$25.0814	$25.08	$25.10	$25.10
Purchase #6	$215.30	3.447%	$222.7214	$222.72	$222.70	$222.70
Purchase #7	$33.50	10.848%	$37.1341	$37.13	$37.15	$37.10
7 purchase totals =	$979.96		$1,052.2624	$1,052.25	$1,052.25	$1,052.20