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	$40.66	11.246%	$45.2326	$45.23	$45.25	$45.20
Purchase #2	$155.82	4.268%	$162.4704	$162.47	$162.45	$162.50
Purchase #3	$54.89	4.681%	$57.4594	$57.46	$57.45	$57.50
Purchase #4	$131.79	5.852%	$139.5024	$139.50	$139.50	$139.50
Purchase #5	$231.90	10.236%	$255.6373	$255.64	$255.65	$255.60
Purchase #6	$127.71	8.485%	$138.5462	$138.55	$138.55	$138.50
Purchase #7	$184.75	7.462%	$198.536	$198.54	$198.55	$198.50
7 purchase totals =	$927.52		$997.3843	$997.39	$997.40	$997.30