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	$139.29	8.357%	$150.9305	$150.93	$150.95	$150.90
Purchase #2	$52.53	13.301%	$59.517	$59.52	$59.50	$59.50
Purchase #3	$50.65	6.743%	$54.0653	$54.07	$54.05	$54.10
Purchase #4	$58.90	6.709%	$62.8516	$62.85	$62.85	$62.90
Purchase #5	$41.59	4.790%	$43.5822	$43.58	$43.60	$43.60
Purchase #6	$186.73	9.808%	$205.0445	$205.04	$205.05	$205.00
Purchase #7	$160.26	5.333%	$168.8067	$168.81	$168.80	$168.80
7 purchase totals =	$689.95		$744.7978	$744.80	$744.80	$744.80