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	$47.38	10.544%	$52.3757	$52.38	$52.40	$52.40
Purchase #2	$133.72	9.639%	$146.6093	$146.61	$146.60	$146.60
Purchase #3	$135.53	6.322%	$144.0982	$144.10	$144.10	$144.10
Purchase #4	$51.90	13.781%	$59.0523	$59.05	$59.05	$59.10
Purchase #5	$248.87	10.120%	$274.0556	$274.06	$274.05	$274.10
Purchase #6	$65.81	8.641%	$71.4966	$71.50	$71.50	$71.50
Purchase #7	$227.37	12.855%	$256.5984	$256.60	$256.60	$256.60
7 purchase totals =	$910.58		$1,004.2861	$1,004.30	$1,004.30	$1,004.40