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	$85.77	10.433%	$94.7184	$94.72	$94.70	$94.70
Purchase #2	$122.93	3.572%	$127.3211	$127.32	$127.30	$127.30
Purchase #3	$143.83	3.377%	$148.6871	$148.69	$148.70	$148.70
Purchase #4	$78.25	5.599%	$82.6312	$82.63	$82.65	$82.60
Purchase #5	$89.61	8.397%	$97.1346	$97.13	$97.15	$97.10
Purchase #6	$213.61	9.830%	$234.6079	$234.61	$234.60	$234.60
Purchase #7	$213.67	10.802%	$236.7506	$236.75	$236.75	$236.80
7 purchase totals =	$947.67		$1,021.8509	$1,021.85	$1,021.85	$1,021.80