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	$78.71	4.757%	$82.4542	$82.45	$82.45	$82.50
Purchase #2	$27.76	12.221%	$31.1525	$31.15	$31.15	$31.20
Purchase #3	$198.77	13.825%	$226.25	$226.25	$226.25	$226.30
Purchase #4	$136.55	5.528%	$144.0985	$144.10	$144.10	$144.10
Purchase #5	$88.31	7.818%	$95.2141	$95.21	$95.20	$95.20
Purchase #6	$214.76	8.538%	$233.0962	$233.10	$233.10	$233.10
Purchase #7	$229.41	11.867%	$256.6341	$256.63	$256.65	$256.60
7 purchase totals =	$974.27		$1,068.8996	$1,068.89	$1,068.90	$1,069.00