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	$174.54	13.570%	$198.2251	$198.23	$198.25	$198.20
Purchase #2	$137.64	5.568%	$145.3038	$145.30	$145.30	$145.30
Purchase #3	$94.52	4.717%	$98.9785	$98.98	$99.00	$99.00
Purchase #4	$34.45	10.759%	$38.1565	$38.16	$38.15	$38.20
Purchase #5	$150.52	9.123%	$164.2519	$164.25	$164.25	$164.30
Purchase #6	$111.61	6.256%	$118.5923	$118.59	$118.60	$118.60
Purchase #7	$195.98	7.509%	$210.6961	$210.70	$210.70	$210.70
7 purchase totals =	$899.26		$974.2042	$974.21	$974.25	$974.30