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	$226.26	6.298%	$240.5099	$240.51	$240.50	$240.50
Purchase #2	$184.34	11.535%	$205.6036	$205.60	$205.60	$205.60
Purchase #3	$142.30	7.691%	$153.2443	$153.24	$153.25	$153.20
Purchase #4	$101.58	5.861%	$107.5336	$107.53	$107.55	$107.50
Purchase #5	$53.83	10.603%	$59.5376	$59.54	$59.55	$59.50
Purchase #6	$68.30	4.698%	$71.5087	$71.51	$71.50	$71.50
Purchase #7	$200.37	9.231%	$218.8662	$218.87	$218.85	$218.90
7 purchase totals =	$976.98		$1,056.8039	$1,056.80	$1,056.80	$1,056.70