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	$219.27	5.379%	$231.0645	$231.06	$231.05	$231.10
Purchase #2	$174.46	9.824%	$191.599	$191.60	$191.60	$191.60
Purchase #3	$196.27	13.544%	$222.8528	$222.85	$222.85	$222.90
Purchase #4	$244.49	4.166%	$254.6755	$254.68	$254.70	$254.70
Purchase #5	$47.63	4.715%	$49.8758	$49.88	$49.90	$49.90
Purchase #6	$202.40	9.725%	$222.0834	$222.08	$222.10	$222.10
Purchase #7	$45.77	9.524%	$50.1291	$50.13	$50.15	$50.10
7 purchase totals =	$1,130.29		$1,222.2801	$1,222.28	$1,222.35	$1,222.40