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	$109.25	4.755%	$114.4448	$114.44	$114.45	$114.40
Purchase #2	$230.79	3.265%	$238.3253	$238.33	$238.35	$238.30
Purchase #3	$41.25	3.252%	$42.5915	$42.59	$42.60	$42.60
Purchase #4	$138.90	6.806%	$148.3535	$148.35	$148.35	$148.40
Purchase #5	$141.36	10.285%	$155.8989	$155.90	$155.90	$155.90
Purchase #6	$48.83	8.295%	$52.8804	$52.88	$52.90	$52.90
Purchase #7	$44.98	3.275%	$46.4531	$46.45	$46.45	$46.50
7 purchase totals =	$755.36		$798.9475	$798.94	$799.00	$799.00