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	$248.62	4.787%	$260.5214	$260.52	$260.50	$260.50
Purchase #2	$92.51	12.296%	$103.885	$103.89	$103.90	$103.90
Purchase #3	$9.98	6.116%	$10.5904	$10.59	$10.60	$10.60
Purchase #4	$117.28	6.272%	$124.6358	$124.64	$124.65	$124.60
Purchase #5	$78.62	4.868%	$82.4472	$82.45	$82.45	$82.40
Purchase #6	$103.91	13.553%	$117.9929	$117.99	$118.00	$118.00
Purchase #7	$147.49	13.142%	$166.8731	$166.87	$166.85	$166.90
7 purchase totals =	$798.41		$866.9458	$866.95	$866.95	$866.90