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	$205.40	11.721%	$229.4749	$229.47	$229.45	$229.50
Purchase #2	$167.52	7.193%	$179.5697	$179.57	$179.55	$179.60
Purchase #3	$154.30	8.607%	$167.5806	$167.58	$167.60	$167.60
Purchase #4	$102.78	4.675%	$107.585	$107.59	$107.60	$107.60
Purchase #5	$139.34	3.473%	$144.1793	$144.18	$144.20	$144.20
Purchase #6	$43.85	9.215%	$47.8908	$47.89	$47.90	$47.90
Purchase #7	$161.56	3.789%	$167.6815	$167.68	$167.70	$167.70
7 purchase totals =	$974.75		$1,043.9618	$1,043.96	$1,044.00	$1,044.10