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	$104.99	12.647%	$118.2681	$118.27	$118.25	$118.30
Purchase #2	$20.38	3.547%	$21.1029	$21.10	$21.10	$21.10
Purchase #3	$153.60	12.219%	$172.3684	$172.37	$172.35	$172.40
Purchase #4	$215.92	11.716%	$241.2172	$241.22	$241.20	$241.20
Purchase #5	$64.92	12.254%	$72.8753	$72.88	$72.90	$72.90
Purchase #6	$215.92	4.423%	$225.4701	$225.47	$225.45	$225.50
Purchase #7	$120.81	8.751%	$131.3821	$131.38	$131.40	$131.40
7 purchase totals =	$896.54		$982.6841	$982.69	$982.65	$982.80