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	$164.57	9.713%	$180.5547	$180.55	$180.55	$180.60
Purchase #2	$103.65	9.294%	$113.2832	$113.28	$113.30	$113.30
Purchase #3	$123.26	13.269%	$139.6154	$139.62	$139.60	$139.60
Purchase #4	$10.28	3.428%	$10.6324	$10.63	$10.65	$10.60
Purchase #5	$136.49	6.283%	$145.0657	$145.07	$145.05	$145.10
Purchase #6	$107.33	3.768%	$111.3742	$111.37	$111.35	$111.40
Purchase #7	$47.80	7.419%	$51.3463	$51.35	$51.35	$51.30
7 purchase totals =	$693.38		$751.8719	$751.87	$751.85	$751.90