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	$52.65	13.698%	$59.862	$59.86	$59.85	$59.90
Purchase #2	$246.81	5.858%	$261.2681	$261.27	$261.25	$261.30
Purchase #3	$89.81	11.652%	$100.2747	$100.27	$100.25	$100.30
Purchase #4	$249.96	4.495%	$261.1957	$261.20	$261.20	$261.20
Purchase #5	$139.90	11.681%	$156.2417	$156.24	$156.25	$156.20
Purchase #6	$118.37	13.452%	$134.2931	$134.29	$134.30	$134.30
Purchase #7	$213.41	6.409%	$227.0874	$227.09	$227.10	$227.10
7 purchase totals =	$1,110.91		$1,200.2227	$1,200.22	$1,200.20	$1,200.30