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	$196.75	12.637%	$221.6133	$221.61	$221.60	$221.60
Purchase #2	$129.39	9.144%	$141.2214	$141.22	$141.20	$141.20
Purchase #3	$157.83	5.848%	$167.0599	$167.06	$167.05	$167.10
Purchase #4	$219.92	8.597%	$238.8265	$238.83	$238.85	$238.80
Purchase #5	$72.27	10.874%	$80.1286	$80.13	$80.15	$80.10
Purchase #6	$135.26	5.277%	$142.3977	$142.40	$142.40	$142.40
Purchase #7	$108.85	13.690%	$123.7516	$123.75	$123.75	$123.80
7 purchase totals =	$1,020.27		$1,114.9990	$1,115.00	$1,115.00	$1,115.00