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	$232.67	10.513%	$257.1306	$257.13	$257.15	$257.10
Purchase #2	$29.59	7.189%	$31.7172	$31.72	$31.70	$31.70
Purchase #3	$93.43	5.113%	$98.2071	$98.21	$98.20	$98.20
Purchase #4	$145.25	8.861%	$158.1206	$158.12	$158.10	$158.10
Purchase #5	$95.80	5.253%	$100.8324	$100.83	$100.85	$100.80
Purchase #6	$189.88	4.807%	$199.0075	$199.01	$199.00	$199.00
Purchase #7	$112.79	13.323%	$127.817	$127.82	$127.80	$127.80
7 purchase totals =	$899.41		$972.8324	$972.84	$972.80	$972.70