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	$189.77	13.854%	$216.0607	$216.06	$216.05	$216.10
Purchase #2	$103.49	13.803%	$117.7747	$117.77	$117.75	$117.80
Purchase #3	$194.41	13.372%	$220.4065	$220.41	$220.40	$220.40
Purchase #4	$211.88	5.689%	$223.9339	$223.93	$223.95	$223.90
Purchase #5	$134.79	5.673%	$142.4366	$142.44	$142.45	$142.40
Purchase #6	$150.51	7.392%	$161.6357	$161.64	$161.65	$161.60
Purchase #7	$85.50	5.808%	$90.4658	$90.47	$90.45	$90.50
7 purchase totals =	$1,070.35		$1,172.7139	$1,172.72	$1,172.70	$1,172.70