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	$79.41	7.679%	$85.5079	$85.51	$85.50	$85.50
Purchase #2	$182.33	11.867%	$203.9671	$203.97	$203.95	$204.00
Purchase #3	$44.85	13.169%	$50.7563	$50.76	$50.75	$50.80
Purchase #4	$139.68	3.196%	$144.1442	$144.14	$144.15	$144.10
Purchase #5	$181.79	9.397%	$198.8728	$198.87	$198.85	$198.90
Purchase #6	$117.65	8.631%	$127.8044	$127.80	$127.80	$127.80
Purchase #7	$174.58	10.839%	$193.5027	$193.50	$193.50	$193.50
7 purchase totals =	$920.29		$1,004.5554	$1,004.55	$1,004.50	$1,004.60