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	$248.96	8.613%	$270.4029	$270.40	$270.40	$270.40
Purchase #2	$41.96	9.712%	$46.0352	$46.04	$46.05	$46.00
Purchase #3	$230.93	8.558%	$250.693	$250.69	$250.70	$250.70
Purchase #4	$30.46	9.404%	$33.3245	$33.32	$33.30	$33.30
Purchase #5	$145.33	3.509%	$150.4296	$150.43	$150.45	$150.40
Purchase #6	$138.42	10.868%	$153.4635	$153.46	$153.45	$153.50
Purchase #7	$201.98	10.253%	$222.689	$222.69	$222.70	$222.70
7 purchase totals =	$1,038.04		$1,127.0377	$1,127.03	$1,127.05	$1,127.00