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	$162.90	13.561%	$184.9909	$184.99	$185.00	$185.00
Purchase #2	$86.56	11.600%	$96.601	$96.60	$96.60	$96.60
Purchase #3	$187.56	8.376%	$203.27	$203.27	$203.25	$203.30
Purchase #4	$37.92	7.726%	$40.8497	$40.85	$40.85	$40.80
Purchase #5	$206.64	3.789%	$214.4696	$214.47	$214.45	$214.50
Purchase #6	$64.55	11.765%	$72.1443	$72.14	$72.15	$72.10
Purchase #7	$230.30	12.554%	$259.2119	$259.21	$259.20	$259.20
7 purchase totals =	$976.43		$1,071.5374	$1,071.53	$1,071.50	$1,071.50