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	$137.25	6.670%	$146.4046	$146.40	$146.40	$146.40
Purchase #2	$75.67	4.197%	$78.8459	$78.85	$78.85	$78.80
Purchase #3	$30.63	4.790%	$32.0972	$32.10	$32.10	$32.10
Purchase #4	$30.27	7.197%	$32.4485	$32.45	$32.45	$32.40
Purchase #5	$182.62	8.513%	$198.1664	$198.17	$198.15	$198.20
Purchase #6	$113.47	11.299%	$126.291	$126.29	$126.30	$126.30
Purchase #7	$86.49	10.520%	$95.5887	$95.59	$95.60	$95.60
7 purchase totals =	$656.40		$709.8423	$709.85	$709.85	$709.80