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	$183.60	13.172%	$207.7838	$207.78	$207.80	$207.80
Purchase #2	$123.48	6.567%	$131.5889	$131.59	$131.60	$131.60
Purchase #3	$188.80	8.315%	$204.4987	$204.50	$204.50	$204.50
Purchase #4	$222.78	3.810%	$231.2679	$231.27	$231.25	$231.30
Purchase #5	$178.69	11.585%	$199.3912	$199.39	$199.40	$199.40
Purchase #6	$119.48	5.866%	$126.4887	$126.49	$126.50	$126.50
Purchase #7	$223.50	9.354%	$244.4062	$244.41	$244.40	$244.40
7 purchase totals =	$1,240.33		$1,345.4254	$1,345.43	$1,345.45	$1,345.50