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	$195.60	11.728%	$218.54	$218.54	$218.55	$218.50
Purchase #2	$233.92	9.699%	$256.6079	$256.61	$256.60	$256.60
Purchase #3	$86.74	10.777%	$96.088	$96.09	$96.10	$96.10
Purchase #4	$38.50	12.629%	$43.3622	$43.36	$43.35	$43.40
Purchase #5	$56.47	12.233%	$63.378	$63.38	$63.40	$63.40
Purchase #6	$228.30	5.567%	$241.0095	$241.01	$241.00	$241.00
Purchase #7	$133.88	9.445%	$146.525	$146.53	$146.55	$146.50
7 purchase totals =	$973.41		$1,065.5106	$1,065.52	$1,065.55	$1,065.50