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	$56.58	4.557%	$59.1584	$59.16	$59.15	$59.20
Purchase #2	$198.88	7.593%	$213.981	$213.98	$214.00	$214.00
Purchase #3	$61.68	6.643%	$65.7774	$65.78	$65.80	$65.80
Purchase #4	$165.50	6.200%	$175.761	$175.76	$175.75	$175.80
Purchase #5	$34.32	12.297%	$38.5403	$38.54	$38.55	$38.50
Purchase #6	$108.42	9.383%	$118.593	$118.59	$118.60	$118.60
Purchase #7	$178.93	4.395%	$186.794	$186.79	$186.80	$186.80
7 purchase totals =	$804.31		$858.6051	$858.60	$858.65	$858.70