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	$85.96	12.167%	$96.4188	$96.42	$96.40	$96.40
Purchase #2	$244.46	12.293%	$274.5115	$274.51	$274.50	$274.50
Purchase #3	$48.75	9.773%	$53.5143	$53.51	$53.50	$53.50
Purchase #4	$145.65	4.105%	$151.6289	$151.63	$151.65	$151.60
Purchase #5	$57.73	9.341%	$63.1226	$63.12	$63.10	$63.10
Purchase #6	$195.39	13.498%	$221.7637	$221.76	$221.75	$221.80
Purchase #7	$226.40	12.660%	$255.0622	$255.06	$255.05	$255.10
7 purchase totals =	$1,004.34		$1,116.0220	$1,116.01	$1,115.95	$1,116.00