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	$85.37	4.464%	$89.1809	$89.18	$89.20	$89.20
Purchase #2	$207.62	4.845%	$217.6792	$217.68	$217.70	$217.70
Purchase #3	$116.82	3.368%	$120.7545	$120.75	$120.75	$120.80
Purchase #4	$224.53	10.582%	$248.2898	$248.29	$248.30	$248.30
Purchase #5	$16.32	5.632%	$17.2391	$17.24	$17.25	$17.20
Purchase #6	$123.30	7.801%	$132.9186	$132.92	$132.90	$132.90
Purchase #7	$237.64	7.471%	$255.3941	$255.39	$255.40	$255.40
7 purchase totals =	$1,011.60		$1,081.4562	$1,081.45	$1,081.50	$1,081.50