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	$152.27	9.719%	$167.0691	$167.07	$167.05	$167.10
Purchase #2	$173.90	6.497%	$185.1983	$185.20	$185.20	$185.20
Purchase #3	$102.90	9.474%	$112.6487	$112.65	$112.65	$112.60
Purchase #4	$46.94	9.721%	$51.503	$51.50	$51.50	$51.50
Purchase #5	$27.95	5.356%	$29.447	$29.45	$29.45	$29.40
Purchase #6	$212.26	5.479%	$223.8897	$223.89	$223.90	$223.90
Purchase #7	$79.85	13.296%	$90.4669	$90.47	$90.45	$90.50
7 purchase totals =	$796.07		$860.2227	$860.23	$860.20	$860.20