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	$94.31	7.588%	$101.4662	$101.47	$101.45	$101.50
Purchase #2	$87.66	10.271%	$96.6636	$96.66	$96.65	$96.70
Purchase #3	$139.43	3.800%	$144.7283	$144.73	$144.75	$144.70
Purchase #4	$217.67	7.464%	$233.9169	$233.92	$233.90	$233.90
Purchase #5	$114.73	10.764%	$127.0795	$127.08	$127.10	$127.10
Purchase #6	$56.72	4.813%	$59.4499	$59.45	$59.45	$59.40
Purchase #7	$235.40	10.826%	$260.8844	$260.88	$260.90	$260.90
7 purchase totals =	$945.92		$1,024.1888	$1,024.19	$1,024.20	$1,024.20