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	$144.53	4.632%	$151.2246	$151.22	$151.20	$151.20
Purchase #2	$209.93	5.424%	$221.3166	$221.32	$221.30	$221.30
Purchase #3	$222.92	10.588%	$246.5228	$246.52	$246.50	$246.50
Purchase #4	$39.31	9.622%	$43.0924	$43.09	$43.10	$43.10
Purchase #5	$224.27	5.376%	$236.3268	$236.33	$236.35	$236.30
Purchase #6	$59.42	12.810%	$67.0317	$67.03	$67.05	$67.00
Purchase #7	$167.52	5.714%	$177.0921	$177.09	$177.10	$177.10
7 purchase totals =	$1,067.90		$1,142.6070	$1,142.60	$1,142.60	$1,142.50