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	$100.83	13.535%	$114.4773	$114.48	$114.50	$114.50
Purchase #2	$56.62	5.364%	$59.6571	$59.66	$59.65	$59.70
Purchase #3	$123.91	6.344%	$131.7709	$131.77	$131.75	$131.80
Purchase #4	$63.96	3.404%	$66.1372	$66.14	$66.15	$66.10
Purchase #5	$230.89	3.622%	$239.2528	$239.25	$239.25	$239.30
Purchase #6	$198.93	4.419%	$207.7207	$207.72	$207.70	$207.70
Purchase #7	$98.80	11.773%	$110.4317	$110.43	$110.45	$110.40
7 purchase totals =	$873.94		$929.4477	$929.45	$929.45	$929.50