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	$99.25	12.514%	$111.6701	$111.67	$111.65	$111.70
Purchase #2	$153.94	5.239%	$162.0049	$162.00	$162.00	$162.00
Purchase #3	$168.99	7.507%	$181.6761	$181.68	$181.70	$181.70
Purchase #4	$29.65	10.742%	$32.835	$32.84	$32.85	$32.80
Purchase #5	$170.47	4.634%	$178.3696	$178.37	$178.35	$178.40
Purchase #6	$67.44	6.736%	$71.9828	$71.98	$72.00	$72.00
Purchase #7	$211.54	9.391%	$231.4057	$231.41	$231.40	$231.40
7 purchase totals =	$901.28		$969.9442	$969.95	$969.95	$970.00