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	$174.92	6.856%	$186.9125	$186.91	$186.90	$186.90
Purchase #2	$105.69	5.123%	$111.1045	$111.10	$111.10	$111.10
Purchase #3	$72.41	12.766%	$81.6539	$81.65	$81.65	$81.70
Purchase #4	$87.51	8.232%	$94.7138	$94.71	$94.70	$94.70
Purchase #5	$151.38	4.682%	$158.4676	$158.47	$158.45	$158.50
Purchase #6	$164.56	11.115%	$182.8508	$182.85	$182.85	$182.90
Purchase #7	$85.82	11.519%	$95.7056	$95.71	$95.70	$95.70
7 purchase totals =	$842.29		$911.4087	$911.40	$911.35	$911.50