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	$105.58	12.846%	$119.1428	$119.14	$119.15	$119.10
Purchase #2	$78.71	11.254%	$87.568	$87.57	$87.55	$87.60
Purchase #3	$9.54	9.555%	$10.4515	$10.45	$10.45	$10.50
Purchase #4	$208.39	9.127%	$227.4098	$227.41	$227.40	$227.40
Purchase #5	$57.68	3.321%	$59.5956	$59.60	$59.60	$59.60
Purchase #6	$201.41	10.439%	$222.4352	$222.44	$222.45	$222.40
Purchase #7	$42.95	8.216%	$46.4788	$46.48	$46.50	$46.50
7 purchase totals =	$704.26		$773.0817	$773.09	$773.10	$773.10