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	$132.56	7.185%	$142.0844	$142.08	$142.10	$142.10
Purchase #2	$40.62	9.587%	$44.5142	$44.51	$44.50	$44.50
Purchase #3	$215.60	5.392%	$227.2252	$227.23	$227.25	$227.20
Purchase #4	$80.82	9.359%	$88.3839	$88.38	$88.40	$88.40
Purchase #5	$119.49	10.825%	$132.4248	$132.42	$132.40	$132.40
Purchase #6	$122.34	4.397%	$127.7193	$127.72	$127.70	$127.70
Purchase #7	$250.62	10.726%	$277.5015	$277.50	$277.50	$277.50
7 purchase totals =	$962.05		$1,039.8533	$1,039.84	$1,039.85	$1,039.80