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	$220.85	12.693%	$248.8825	$248.88	$248.90	$248.90
Purchase #2	$233.58	9.188%	$255.0413	$255.04	$255.05	$255.00
Purchase #3	$41.69	13.498%	$47.3173	$47.32	$47.30	$47.30
Purchase #4	$154.90	7.611%	$166.6894	$166.69	$166.70	$166.70
Purchase #5	$71.81	11.850%	$80.3195	$80.32	$80.30	$80.30
Purchase #6	$21.95	13.725%	$24.9626	$24.96	$24.95	$25.00
Purchase #7	$190.51	4.523%	$199.1268	$199.13	$199.15	$199.10
7 purchase totals =	$935.29		$1,022.3394	$1,022.34	$1,022.35	$1,022.30