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	$62.52	4.334%	$65.2296	$65.23	$65.25	$65.20
Purchase #2	$175.81	11.182%	$195.4691	$195.47	$195.45	$195.50
Purchase #3	$70.31	12.143%	$78.8477	$78.85	$78.85	$78.80
Purchase #4	$107.66	4.817%	$112.846	$112.85	$112.85	$112.80
Purchase #5	$20.69	5.525%	$21.8331	$21.83	$21.85	$21.80
Purchase #6	$26.67	5.294%	$28.0819	$28.08	$28.10	$28.10
Purchase #7	$45.43	11.380%	$50.5999	$50.60	$50.60	$50.60
7 purchase totals =	$509.09		$552.9073	$552.91	$552.95	$552.80