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	$107.42	8.685%	$116.7494	$116.75	$116.75	$116.70
Purchase #2	$43.82	10.675%	$48.4978	$48.50	$48.50	$48.50
Purchase #3	$225.89	11.183%	$251.1513	$251.15	$251.15	$251.20
Purchase #4	$112.79	3.576%	$116.8234	$116.82	$116.80	$116.80
Purchase #5	$148.83	5.118%	$156.4471	$156.45	$156.45	$156.40
Purchase #6	$182.45	7.111%	$195.424	$195.42	$195.40	$195.40
Purchase #7	$145.44	9.643%	$159.4648	$159.46	$159.45	$159.50
7 purchase totals =	$966.64		$1,044.5578	$1,044.55	$1,044.50	$1,044.50