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	$206.78	11.732%	$231.0394	$231.04	$231.05	$231.00
Purchase #2	$54.58	8.262%	$59.0894	$59.09	$59.10	$59.10
Purchase #3	$74.78	9.743%	$82.0658	$82.07	$82.05	$82.10
Purchase #4	$223.78	6.590%	$238.5271	$238.53	$238.55	$238.50
Purchase #5	$140.31	6.738%	$149.7641	$149.76	$149.75	$149.80
Purchase #6	$97.37	12.323%	$109.3689	$109.37	$109.35	$109.40
Purchase #7	$167.85	10.475%	$185.4323	$185.43	$185.45	$185.40
7 purchase totals =	$965.45		$1,055.2870	$1,055.29	$1,055.30	$1,055.30