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	$110.89	11.309%	$123.4306	$123.43	$123.45	$123.40
Purchase #2	$182.63	11.725%	$204.0434	$204.04	$204.05	$204.00
Purchase #3	$102.41	9.189%	$111.8205	$111.82	$111.80	$111.80
Purchase #4	$160.60	9.478%	$175.8217	$175.82	$175.80	$175.80
Purchase #5	$97.27	10.552%	$107.5339	$107.53	$107.55	$107.50
Purchase #6	$200.53	6.261%	$213.0852	$213.09	$213.10	$213.10
Purchase #7	$154.95	3.779%	$160.8056	$160.81	$160.80	$160.80
7 purchase totals =	$1,009.28		$1,096.5409	$1,096.54	$1,096.55	$1,096.40