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	$153.37	13.377%	$173.8863	$173.89	$173.90	$173.90
Purchase #2	$117.95	8.288%	$127.7257	$127.73	$127.75	$127.70
Purchase #3	$91.43	12.727%	$103.0663	$103.07	$103.05	$103.10
Purchase #4	$173.34	3.768%	$179.8715	$179.87	$179.85	$179.90
Purchase #5	$88.47	4.527%	$92.475	$92.48	$92.50	$92.50
Purchase #6	$217.59	3.195%	$224.542	$224.54	$224.55	$224.50
Purchase #7	$128.79	9.187%	$140.6219	$140.62	$140.60	$140.60
7 purchase totals =	$970.94		$1,042.1887	$1,042.20	$1,042.20	$1,042.20