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	$135.74	6.469%	$144.521	$144.52	$144.50	$144.50
Purchase #2	$58.70	5.153%	$61.7248	$61.72	$61.70	$61.70
Purchase #3	$22.77	3.295%	$23.5203	$23.52	$23.50	$23.50
Purchase #4	$121.99	3.335%	$126.0584	$126.06	$126.05	$126.10
Purchase #5	$114.96	11.132%	$127.7573	$127.76	$127.75	$127.80
Purchase #6	$57.82	11.709%	$64.5901	$64.59	$64.60	$64.60
Purchase #7	$59.80	8.510%	$64.889	$64.89	$64.90	$64.90
7 purchase totals =	$571.78		$613.0609	$613.06	$613.00	$613.10