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	$100.73	11.633%	$112.4479	$112.45	$112.45	$112.40
Purchase #2	$112.68	13.853%	$128.2896	$128.29	$128.30	$128.30
Purchase #3	$178.43	7.557%	$191.914	$191.91	$191.90	$191.90
Purchase #4	$48.62	13.205%	$55.0403	$55.04	$55.05	$55.00
Purchase #5	$226.97	6.442%	$241.5914	$241.59	$241.60	$241.60
Purchase #6	$42.53	8.496%	$46.1433	$46.14	$46.15	$46.10
Purchase #7	$23.75	7.737%	$25.5875	$25.59	$25.60	$25.60
7 purchase totals =	$733.71		$801.0140	$801.01	$801.05	$800.90