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	$212.71	4.526%	$222.3373	$222.34	$222.35	$222.30
Purchase #2	$145.69	12.837%	$164.3922	$164.39	$164.40	$164.40
Purchase #3	$160.98	8.854%	$175.2332	$175.23	$175.25	$175.20
Purchase #4	$107.25	11.109%	$119.1644	$119.16	$119.15	$119.20
Purchase #5	$144.70	9.294%	$158.1484	$158.15	$158.15	$158.10
Purchase #6	$61.45	5.319%	$64.7185	$64.72	$64.70	$64.70
Purchase #7	$75.84	6.275%	$80.599	$80.60	$80.60	$80.60
7 purchase totals =	$908.62		$984.5930	$984.59	$984.60	$984.50