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	$93.60	6.426%	$99.6147	$99.61	$99.60	$99.60
Purchase #2	$127.55	3.805%	$132.4033	$132.40	$132.40	$132.40
Purchase #3	$60.48	13.262%	$68.5009	$68.50	$68.50	$68.50
Purchase #4	$29.99	12.208%	$33.6512	$33.65	$33.65	$33.70
Purchase #5	$112.35	10.866%	$124.558	$124.56	$124.55	$124.60
Purchase #6	$188.48	13.327%	$213.5987	$213.60	$213.60	$213.60
Purchase #7	$96.29	4.572%	$100.6924	$100.69	$100.70	$100.70
7 purchase totals =	$708.74		$773.0192	$773.01	$773.00	$773.10