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	$222.56	11.658%	$248.506	$248.51	$248.50	$248.50
Purchase #2	$158.72	12.633%	$178.7711	$178.77	$178.75	$178.80
Purchase #3	$92.72	12.114%	$103.9521	$103.95	$103.95	$104.00
Purchase #4	$98.95	6.499%	$105.3808	$105.38	$105.40	$105.40
Purchase #5	$126.53	12.143%	$141.8945	$141.89	$141.90	$141.90
Purchase #6	$15.37	5.554%	$16.2236	$16.22	$16.20	$16.20
Purchase #7	$88.68	4.287%	$92.4817	$92.48	$92.50	$92.50
7 purchase totals =	$803.53		$887.2098	$887.20	$887.20	$887.30