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	$45.62	5.170%	$47.9786	$47.98	$48.00	$48.00
Purchase #2	$156.40	7.776%	$168.5617	$168.56	$168.55	$168.60
Purchase #3	$139.89	7.382%	$150.2167	$150.22	$150.20	$150.20
Purchase #4	$137.49	4.276%	$143.3691	$143.37	$143.35	$143.40
Purchase #5	$172.55	7.258%	$185.0737	$185.07	$185.05	$185.10
Purchase #6	$148.78	10.528%	$164.4436	$164.44	$164.45	$164.40
Purchase #7	$148.59	13.455%	$168.5828	$168.58	$168.60	$168.60
7 purchase totals =	$949.32		$1,028.2262	$1,028.22	$1,028.20	$1,028.30