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	$217.61	10.102%	$239.593	$239.59	$239.60	$239.60
Purchase #2	$25.76	9.239%	$28.14	$28.14	$28.15	$28.10
Purchase #3	$98.95	5.723%	$104.6129	$104.61	$104.60	$104.60
Purchase #4	$235.32	4.543%	$246.0106	$246.01	$246.00	$246.00
Purchase #5	$17.40	7.297%	$18.6697	$18.67	$18.65	$18.70
Purchase #6	$117.74	4.700%	$123.2738	$123.27	$123.25	$123.30
Purchase #7	$192.37	13.557%	$218.4496	$218.45	$218.45	$218.40
7 purchase totals =	$905.15		$978.7496	$978.74	$978.70	$978.70