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	$119.30	4.679%	$124.882	$124.88	$124.90	$124.90
Purchase #2	$40.79	10.793%	$45.1925	$45.19	$45.20	$45.20
Purchase #3	$61.46	7.511%	$66.0763	$66.08	$66.10	$66.10
Purchase #4	$245.41	12.671%	$276.5059	$276.51	$276.50	$276.50
Purchase #5	$180.60	8.246%	$195.4923	$195.49	$195.50	$195.50
Purchase #6	$228.33	4.833%	$239.3652	$239.37	$239.35	$239.40
Purchase #7	$57.95	3.397%	$59.9186	$59.92	$59.90	$59.90
7 purchase totals =	$933.84		$1,007.4328	$1,007.44	$1,007.45	$1,007.50