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	$60.54	4.284%	$63.1335	$63.13	$63.15	$63.10
Purchase #2	$54.92	7.507%	$59.0428	$59.04	$59.05	$59.00
Purchase #3	$134.94	12.348%	$151.6024	$151.60	$151.60	$151.60
Purchase #4	$204.47	6.863%	$218.5028	$218.50	$218.50	$218.50
Purchase #5	$93.99	11.782%	$105.0639	$105.06	$105.05	$105.10
Purchase #6	$117.58	8.529%	$127.6084	$127.61	$127.60	$127.60
Purchase #7	$134.58	5.683%	$142.2282	$142.23	$142.25	$142.20
7 purchase totals =	$801.02		$867.1820	$867.17	$867.20	$867.10