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	$164.68	5.590%	$173.8856	$173.89	$173.90	$173.90
Purchase #2	$223.84	8.365%	$242.5642	$242.56	$242.55	$242.60
Purchase #3	$161.40	12.418%	$181.4427	$181.44	$181.45	$181.40
Purchase #4	$235.83	8.741%	$256.4439	$256.44	$256.45	$256.40
Purchase #5	$43.89	10.319%	$48.419	$48.42	$48.40	$48.40
Purchase #6	$225.40	3.591%	$233.4941	$233.49	$233.50	$233.50
Purchase #7	$235.90	12.446%	$265.2601	$265.26	$265.25	$265.30
7 purchase totals =	$1,290.94		$1,401.5096	$1,401.50	$1,401.50	$1,401.50