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	$35.59	6.669%	$37.9635	$37.96	$37.95	$38.00
Purchase #2	$60.30	8.436%	$65.3869	$65.39	$65.40	$65.40
Purchase #3	$212.83	6.854%	$227.4174	$227.42	$227.40	$227.40
Purchase #4	$47.30	8.314%	$51.2325	$51.23	$51.25	$51.20
Purchase #5	$230.86	11.146%	$256.5917	$256.59	$256.60	$256.60
Purchase #6	$26.29	6.390%	$27.9699	$27.97	$27.95	$28.00
Purchase #7	$68.95	11.558%	$76.9192	$76.92	$76.90	$76.90
7 purchase totals =	$682.12		$743.4811	$743.48	$743.45	$743.50