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	$214.95	13.286%	$243.5083	$243.51	$243.50	$243.50
Purchase #2	$161.83	10.126%	$178.2169	$178.22	$178.20	$178.20
Purchase #3	$53.52	8.111%	$57.861	$57.86	$57.85	$57.90
Purchase #4	$99.78	12.541%	$112.2934	$112.29	$112.30	$112.30
Purchase #5	$117.80	9.728%	$129.2596	$129.26	$129.25	$129.30
Purchase #6	$101.40	12.749%	$114.3275	$114.33	$114.35	$114.30
Purchase #7	$69.54	4.653%	$72.7757	$72.78	$72.80	$72.80
7 purchase totals =	$818.82		$908.2424	$908.25	$908.25	$908.30