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	$115.73	10.181%	$127.5125	$127.51	$127.50	$127.50
Purchase #2	$32.67	3.863%	$33.932	$33.93	$33.95	$33.90
Purchase #3	$84.90	3.148%	$87.5727	$87.57	$87.55	$87.60
Purchase #4	$214.48	11.569%	$239.2932	$239.29	$239.30	$239.30
Purchase #5	$62.70	4.447%	$65.4883	$65.49	$65.50	$65.50
Purchase #6	$43.42	11.837%	$48.5596	$48.56	$48.55	$48.60
Purchase #7	$155.42	12.360%	$174.6299	$174.63	$174.65	$174.60
7 purchase totals =	$709.32		$776.9882	$776.98	$777.00	$777.00