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	$208.31	9.748%	$228.6161	$228.62	$228.60	$228.60
Purchase #2	$145.56	13.472%	$165.1698	$165.17	$165.15	$165.20
Purchase #3	$41.90	7.620%	$45.0928	$45.09	$45.10	$45.10
Purchase #4	$23.96	13.348%	$27.1582	$27.16	$27.15	$27.20
Purchase #5	$155.70	6.650%	$166.0541	$166.05	$166.05	$166.10
Purchase #6	$210.64	12.436%	$236.8352	$236.84	$236.85	$236.80
Purchase #7	$213.62	12.594%	$240.5233	$240.52	$240.50	$240.50
7 purchase totals =	$999.69		$1,109.4495	$1,109.45	$1,109.40	$1,109.50