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	$178.36	9.453%	$195.2204	$195.22	$195.20	$195.20
Purchase #2	$95.78	10.424%	$105.7641	$105.76	$105.75	$105.80
Purchase #3	$107.77	3.776%	$111.8394	$111.84	$111.85	$111.80
Purchase #4	$217.69	4.742%	$228.0129	$228.01	$228.00	$228.00
Purchase #5	$60.52	7.814%	$65.249	$65.25	$65.25	$65.20
Purchase #6	$139.67	3.526%	$144.5948	$144.59	$144.60	$144.60
Purchase #7	$121.87	5.216%	$128.2267	$128.23	$128.25	$128.20
7 purchase totals =	$921.66		$978.9073	$978.90	$978.90	$978.80