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	$54.54	9.683%	$59.8211	$59.82	$59.80	$59.80
Purchase #2	$129.30	12.520%	$145.4884	$145.49	$145.50	$145.50
Purchase #3	$19.58	6.531%	$20.8588	$20.86	$20.85	$20.90
Purchase #4	$164.41	8.799%	$178.8764	$178.88	$178.90	$178.90
Purchase #5	$7.31	4.284%	$7.6232	$7.62	$7.60	$7.60
Purchase #6	$80.27	8.259%	$86.8995	$86.90	$86.90	$86.90
Purchase #7	$23.82	10.253%	$26.2623	$26.26	$26.25	$26.30
7 purchase totals =	$479.23		$525.8297	$525.83	$525.80	$525.90