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	$46.96	12.811%	$52.976	$52.98	$53.00	$53.00
Purchase #2	$35.25	3.761%	$36.5758	$36.58	$36.60	$36.60
Purchase #3	$142.98	6.229%	$151.8862	$151.89	$151.90	$151.90
Purchase #4	$146.98	3.783%	$152.5403	$152.54	$152.55	$152.50
Purchase #5	$59.71	6.110%	$63.3583	$63.36	$63.35	$63.40
Purchase #6	$34.87	5.506%	$36.7899	$36.79	$36.80	$36.80
Purchase #7	$66.29	4.562%	$69.3141	$69.31	$69.30	$69.30
7 purchase totals =	$533.04		$563.4406	$563.45	$563.50	$563.50