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	$231.28	9.328%	$252.8538	$252.85	$252.85	$252.90
Purchase #2	$87.72	7.410%	$94.2201	$94.22	$94.20	$94.20
Purchase #3	$182.25	4.124%	$189.766	$189.77	$189.75	$189.80
Purchase #4	$66.31	9.762%	$72.7832	$72.78	$72.80	$72.80
Purchase #5	$240.37	5.769%	$254.2369	$254.24	$254.25	$254.20
Purchase #6	$131.64	4.300%	$137.3005	$137.30	$137.30	$137.30
Purchase #7	$115.66	12.635%	$130.2736	$130.27	$130.25	$130.30
7 purchase totals =	$1,055.23		$1,131.4341	$1,131.43	$1,131.40	$1,131.50