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	$178.42	7.426%	$191.6695	$191.67	$191.65	$191.70
Purchase #2	$84.86	5.223%	$89.2922	$89.29	$89.30	$89.30
Purchase #3	$166.97	3.517%	$172.8423	$172.84	$172.85	$172.80
Purchase #4	$170.54	3.567%	$176.6232	$176.62	$176.60	$176.60
Purchase #5	$136.91	13.382%	$155.2313	$155.23	$155.25	$155.20
Purchase #6	$172.75	5.572%	$182.3756	$182.38	$182.40	$182.40
Purchase #7	$138.31	9.591%	$151.5753	$151.58	$151.60	$151.60
7 purchase totals =	$1,048.76		$1,119.6094	$1,119.61	$1,119.65	$1,119.60