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	$210.32	11.734%	$234.9989	$235.00	$235.00	$235.00
Purchase #2	$122.39	3.669%	$126.8805	$126.88	$126.90	$126.90
Purchase #3	$66.62	7.279%	$71.4693	$71.47	$71.45	$71.50
Purchase #4	$90.52	13.534%	$102.771	$102.77	$102.75	$102.80
Purchase #5	$93.41	7.570%	$100.4811	$100.48	$100.50	$100.50
Purchase #6	$43.90	4.565%	$45.904	$45.90	$45.90	$45.90
Purchase #7	$124.87	6.593%	$133.1027	$133.10	$133.10	$133.10
7 purchase totals =	$752.03		$815.6075	$815.60	$815.60	$815.70