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	$168.90	13.277%	$191.3249	$191.32	$191.30	$191.30
Purchase #2	$236.51	3.618%	$245.0669	$245.07	$245.05	$245.10
Purchase #3	$117.30	4.524%	$122.6067	$122.61	$122.60	$122.60
Purchase #4	$51.35	9.853%	$56.4095	$56.41	$56.40	$56.40
Purchase #5	$80.95	12.575%	$91.1295	$91.13	$91.15	$91.10
Purchase #6	$185.94	5.601%	$196.3545	$196.35	$196.35	$196.40
Purchase #7	$151.27	10.457%	$167.0883	$167.09	$167.10	$167.10
7 purchase totals =	$992.22		$1,069.9803	$1,069.98	$1,069.95	$1,070.00