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	$244.52	9.407%	$267.522	$267.52	$267.50	$267.50
Purchase #2	$56.55	4.443%	$59.0625	$59.06	$59.05	$59.10
Purchase #3	$247.41	5.523%	$261.0745	$261.07	$261.05	$261.10
Purchase #4	$23.37	4.230%	$24.3586	$24.36	$24.35	$24.40
Purchase #5	$223.76	9.686%	$245.4334	$245.43	$245.45	$245.40
Purchase #6	$31.42	10.214%	$34.6292	$34.63	$34.65	$34.60
Purchase #7	$167.39	3.712%	$173.6035	$173.60	$173.60	$173.60
7 purchase totals =	$994.42		$1,065.6837	$1,065.67	$1,065.65	$1,065.70