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	$106.67	6.402%	$113.499	$113.50	$113.50	$113.50
Purchase #2	$79.87	8.287%	$86.4888	$86.49	$86.50	$86.50
Purchase #3	$172.71	10.669%	$191.1364	$191.14	$191.15	$191.10
Purchase #4	$140.73	13.191%	$159.2937	$159.29	$159.30	$159.30
Purchase #5	$67.94	4.621%	$71.0795	$71.08	$71.10	$71.10
Purchase #6	$30.94	3.449%	$32.0071	$32.01	$32.00	$32.00
Purchase #7	$207.37	3.724%	$215.0925	$215.09	$215.10	$215.10
7 purchase totals =	$806.23		$868.5970	$868.60	$868.65	$868.60