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	$158.77	9.742%	$174.2374	$174.24	$174.25	$174.20
Purchase #2	$247.85	10.551%	$274.0007	$274.00	$274.00	$274.00
Purchase #3	$121.89	5.472%	$128.5598	$128.56	$128.55	$128.60
Purchase #4	$39.52	4.507%	$41.3012	$41.30	$41.30	$41.30
Purchase #5	$31.70	10.206%	$34.9353	$34.94	$34.95	$34.90
Purchase #6	$45.85	5.196%	$48.2324	$48.23	$48.25	$48.20
Purchase #7	$103.94	5.163%	$109.3064	$109.31	$109.30	$109.30
7 purchase totals =	$749.52		$810.5732	$810.58	$810.60	$810.50