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	$81.58	7.456%	$87.6626	$87.66	$87.65	$87.70
Purchase #2	$227.69	9.615%	$249.5824	$249.58	$249.60	$249.60
Purchase #3	$213.35	4.563%	$223.0852	$223.09	$223.10	$223.10
Purchase #4	$167.52	4.426%	$174.9344	$174.93	$174.95	$174.90
Purchase #5	$74.38	12.111%	$83.3882	$83.39	$83.40	$83.40
Purchase #6	$134.60	11.554%	$150.1517	$150.15	$150.15	$150.20
Purchase #7	$131.59	10.262%	$145.0938	$145.09	$145.10	$145.10
7 purchase totals =	$1,030.71		$1,113.8983	$1,113.89	$1,113.95	$1,114.00