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	$218.69	8.642%	$237.5892	$237.59	$237.60	$237.60
Purchase #2	$52.64	4.144%	$54.8214	$54.82	$54.80	$54.80
Purchase #3	$193.49	7.616%	$208.2262	$208.23	$208.25	$208.20
Purchase #4	$143.72	7.710%	$154.8008	$154.80	$154.80	$154.80
Purchase #5	$247.45	3.446%	$255.9771	$255.98	$256.00	$256.00
Purchase #6	$100.99	9.804%	$110.8911	$110.89	$110.90	$110.90
Purchase #7	$45.59	12.495%	$51.2865	$51.29	$51.30	$51.30
7 purchase totals =	$1,002.57		$1,073.5923	$1,073.60	$1,073.65	$1,073.60