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	$94.93	9.412%	$103.8648	$103.86	$103.85	$103.90
Purchase #2	$138.38	8.700%	$150.4191	$150.42	$150.40	$150.40
Purchase #3	$113.89	4.666%	$119.2041	$119.20	$119.20	$119.20
Purchase #4	$197.90	9.591%	$216.8806	$216.88	$216.90	$216.90
Purchase #5	$47.86	4.238%	$49.8883	$49.89	$49.90	$49.90
Purchase #6	$26.45	10.777%	$29.3005	$29.30	$29.30	$29.30
Purchase #7	$11.82	4.186%	$12.3148	$12.31	$12.30	$12.30
7 purchase totals =	$631.23		$681.8722	$681.86	$681.85	$681.90