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	$41.31	13.405%	$46.8476	$46.85	$46.85	$46.80
Purchase #2	$92.90	7.295%	$99.6771	$99.68	$99.70	$99.70
Purchase #3	$228.45	8.326%	$247.4707	$247.47	$247.45	$247.50
Purchase #4	$34.38	3.314%	$35.5194	$35.52	$35.50	$35.50
Purchase #5	$132.46	4.755%	$138.7585	$138.76	$138.75	$138.80
Purchase #6	$63.41	7.835%	$68.3782	$68.38	$68.40	$68.40
Purchase #7	$70.94	10.142%	$78.1347	$78.13	$78.15	$78.10
7 purchase totals =	$663.85		$714.7862	$714.79	$714.80	$714.80