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	$205.33	11.384%	$228.7048	$228.70	$228.70	$228.70
Purchase #2	$103.57	12.564%	$116.5825	$116.58	$116.60	$116.60
Purchase #3	$42.25	3.311%	$43.6489	$43.65	$43.65	$43.60
Purchase #4	$107.57	11.242%	$119.663	$119.66	$119.65	$119.70
Purchase #5	$181.75	3.839%	$188.7274	$188.73	$188.75	$188.70
Purchase #6	$100.82	11.564%	$112.4788	$112.48	$112.50	$112.50
Purchase #7	$31.87	7.738%	$34.3361	$34.34	$34.35	$34.30
7 purchase totals =	$773.16		$844.1415	$844.14	$844.20	$844.10