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	$162.72	6.256%	$172.8998	$172.90	$172.90	$172.90
Purchase #2	$176.32	12.476%	$198.3177	$198.32	$198.30	$198.30
Purchase #3	$151.49	5.710%	$160.1401	$160.14	$160.15	$160.10
Purchase #4	$228.52	12.334%	$256.7057	$256.71	$256.70	$256.70
Purchase #5	$246.65	9.300%	$269.5885	$269.59	$269.60	$269.60
Purchase #6	$171.66	7.631%	$184.7594	$184.76	$184.75	$184.80
Purchase #7	$59.43	7.358%	$63.8029	$63.80	$63.80	$63.80
7 purchase totals =	$1,196.79		$1,306.2141	$1,306.22	$1,306.20	$1,306.20