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	$240.43	9.578%	$263.4584	$263.46	$263.45	$263.50
Purchase #2	$171.72	9.102%	$187.35	$187.35	$187.35	$187.40
Purchase #3	$61.84	3.755%	$64.1621	$64.16	$64.15	$64.20
Purchase #4	$143.83	3.209%	$148.4455	$148.45	$148.45	$148.40
Purchase #5	$169.68	7.422%	$182.2736	$182.27	$182.25	$182.30
Purchase #6	$247.85	13.547%	$281.4262	$281.43	$281.45	$281.40
Purchase #7	$101.59	11.617%	$113.3917	$113.39	$113.40	$113.40
7 purchase totals =	$1,136.94		$1,240.5075	$1,240.51	$1,240.50	$1,240.60