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	$249.32	4.466%	$260.4546	$260.45	$260.45	$260.50
Purchase #2	$65.96	10.369%	$72.7994	$72.80	$72.80	$72.80
Purchase #3	$135.53	13.612%	$153.9783	$153.98	$154.00	$154.00
Purchase #4	$162.77	13.860%	$185.3299	$185.33	$185.35	$185.30
Purchase #5	$31.73	3.519%	$32.8466	$32.85	$32.85	$32.80
Purchase #6	$108.62	10.247%	$119.7503	$119.75	$119.75	$119.80
Purchase #7	$165.78	12.763%	$186.9385	$186.94	$186.95	$186.90
7 purchase totals =	$919.71		$1,012.0976	$1,012.10	$1,012.15	$1,012.10