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	$145.85	8.278%	$157.9235	$157.92	$157.90	$157.90
Purchase #2	$75.90	7.555%	$81.6342	$81.63	$81.65	$81.60
Purchase #3	$175.78	7.415%	$188.8141	$188.81	$188.80	$188.80
Purchase #4	$61.90	6.531%	$65.9427	$65.94	$65.95	$65.90
Purchase #5	$186.47	5.561%	$196.8396	$196.84	$196.85	$196.80
Purchase #6	$229.36	5.115%	$241.0918	$241.09	$241.10	$241.10
Purchase #7	$108.96	13.359%	$123.516	$123.52	$123.50	$123.50
7 purchase totals =	$984.22		$1,055.7619	$1,055.75	$1,055.75	$1,055.60