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	$9.52	10.830%	$10.551	$10.55	$10.55	$10.60
Purchase #2	$38.47	12.554%	$43.2995	$43.30	$43.30	$43.30
Purchase #3	$68.66	12.472%	$77.2233	$77.22	$77.20	$77.20
Purchase #4	$172.31	7.295%	$184.88	$184.88	$184.90	$184.90
Purchase #5	$44.95	6.424%	$47.8376	$47.84	$47.85	$47.80
Purchase #6	$181.43	5.734%	$191.8332	$191.83	$191.85	$191.80
Purchase #7	$34.90	5.671%	$36.8792	$36.88	$36.90	$36.90
7 purchase totals =	$550.24		$592.5038	$592.50	$592.55	$592.50