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	$30.80	7.424%	$33.0866	$33.09	$33.10	$33.10
Purchase #2	$52.49	6.617%	$55.9633	$55.96	$55.95	$56.00
Purchase #3	$127.82	3.205%	$131.9166	$131.92	$131.90	$131.90
Purchase #4	$104.59	7.434%	$112.3652	$112.37	$112.35	$112.40
Purchase #5	$231.73	10.103%	$255.1417	$255.14	$255.15	$255.10
Purchase #6	$224.46	6.545%	$239.1509	$239.15	$239.15	$239.20
Purchase #7	$91.43	7.676%	$98.4482	$98.45	$98.45	$98.40
7 purchase totals =	$863.32		$926.0725	$926.08	$926.05	$926.10