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	$236.29	7.789%	$254.6946	$254.69	$254.70	$254.70
Purchase #2	$226.60	13.288%	$256.7106	$256.71	$256.70	$256.70
Purchase #3	$103.78	5.759%	$109.7567	$109.76	$109.75	$109.80
Purchase #4	$177.75	11.251%	$197.7487	$197.75	$197.75	$197.70
Purchase #5	$78.67	11.133%	$87.4283	$87.43	$87.45	$87.40
Purchase #6	$132.93	3.252%	$137.2529	$137.25	$137.25	$137.30
Purchase #7	$37.51	12.615%	$42.2419	$42.24	$42.25	$42.20
7 purchase totals =	$993.53		$1,085.8337	$1,085.83	$1,085.85	$1,085.80