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	$148.54	12.576%	$167.2204	$167.22	$167.20	$167.20
Purchase #2	$17.66	3.828%	$18.336	$18.34	$18.35	$18.30
Purchase #3	$164.82	9.473%	$180.4334	$180.43	$180.45	$180.40
Purchase #4	$27.90	11.856%	$31.2078	$31.21	$31.20	$31.20
Purchase #5	$82.87	13.522%	$94.0757	$94.08	$94.10	$94.10
Purchase #6	$73.83	10.810%	$81.811	$81.81	$81.80	$81.80
Purchase #7	$36.94	4.276%	$38.5196	$38.52	$38.50	$38.50
7 purchase totals =	$552.56		$611.6039	$611.61	$611.60	$611.50