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	$24.50	3.383%	$25.3288	$25.33	$25.35	$25.30
Purchase #2	$53.62	11.345%	$59.7032	$59.70	$59.70	$59.70
Purchase #3	$205.77	8.300%	$222.8489	$222.85	$222.85	$222.80
Purchase #4	$155.50	4.682%	$162.7805	$162.78	$162.80	$162.80
Purchase #5	$166.90	5.666%	$176.3566	$176.36	$176.35	$176.40
Purchase #6	$113.25	13.473%	$128.5082	$128.51	$128.50	$128.50
Purchase #7	$232.62	8.577%	$252.5718	$252.57	$252.55	$252.60
7 purchase totals =	$952.16		$1,028.0980	$1,028.10	$1,028.10	$1,028.10