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	$165.31	9.806%	$181.5203	$181.52	$181.50	$181.50
Purchase #2	$119.28	10.308%	$131.5754	$131.58	$131.60	$131.60
Purchase #3	$205.28	3.575%	$212.6188	$212.62	$212.60	$212.60
Purchase #4	$118.33	13.216%	$133.9685	$133.97	$133.95	$134.00
Purchase #5	$210.25	3.788%	$218.2143	$218.21	$218.20	$218.20
Purchase #6	$36.27	5.238%	$38.1698	$38.17	$38.15	$38.20
Purchase #7	$136.86	6.322%	$145.5123	$145.51	$145.50	$145.50
7 purchase totals =	$991.58		$1,061.5794	$1,061.58	$1,061.50	$1,061.60