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	$175.54	11.321%	$195.4129	$195.41	$195.40	$195.40
Purchase #2	$139.80	9.723%	$153.3928	$153.39	$153.40	$153.40
Purchase #3	$217.67	9.371%	$238.0679	$238.07	$238.05	$238.10
Purchase #4	$134.78	13.690%	$153.2314	$153.23	$153.25	$153.20
Purchase #5	$50.53	13.287%	$57.2439	$57.24	$57.25	$57.20
Purchase #6	$78.38	10.294%	$86.4484	$86.45	$86.45	$86.40
Purchase #7	$19.46	10.586%	$21.52	$21.52	$21.50	$21.50
7 purchase totals =	$816.16		$905.3173	$905.31	$905.30	$905.20