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	$212.67	12.162%	$238.5349	$238.53	$238.55	$238.50
Purchase #2	$12.54	11.754%	$14.014	$14.01	$14.00	$14.00
Purchase #3	$127.86	3.265%	$132.0346	$132.03	$132.05	$132.00
Purchase #4	$91.92	8.852%	$100.0568	$100.06	$100.05	$100.10
Purchase #5	$182.29	5.112%	$191.6087	$191.61	$191.60	$191.60
Purchase #6	$145.69	7.121%	$156.0646	$156.06	$156.05	$156.10
Purchase #7	$107.45	9.775%	$117.9532	$117.95	$117.95	$118.00
7 purchase totals =	$880.42		$950.2668	$950.25	$950.25	$950.30