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	$55.94	7.117%	$59.9212	$59.92	$59.90	$59.90
Purchase #2	$95.27	5.591%	$100.5965	$100.60	$100.60	$100.60
Purchase #3	$13.28	7.133%	$14.2273	$14.23	$14.25	$14.20
Purchase #4	$139.74	9.103%	$152.4605	$152.46	$152.45	$152.50
Purchase #5	$98.25	5.675%	$103.8257	$103.83	$103.85	$103.80
Purchase #6	$91.25	12.534%	$102.6873	$102.69	$102.70	$102.70
Purchase #7	$161.46	8.291%	$174.8466	$174.85	$174.85	$174.80
7 purchase totals =	$655.19		$708.5651	$708.58	$708.60	$708.50