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	$190.41	9.424%	$208.3542	$208.35	$208.35	$208.40
Purchase #2	$146.87	3.215%	$151.5919	$151.59	$151.60	$151.60
Purchase #3	$208.96	13.184%	$236.5093	$236.51	$236.50	$236.50
Purchase #4	$38.28	10.493%	$42.2967	$42.30	$42.30	$42.30
Purchase #5	$91.28	13.843%	$103.9159	$103.92	$103.90	$103.90
Purchase #6	$238.73	6.533%	$254.3262	$254.33	$254.35	$254.30
Purchase #7	$65.44	13.151%	$74.046	$74.05	$74.05	$74.00
7 purchase totals =	$979.97		$1,071.0402	$1,071.05	$1,071.05	$1,071.00