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	$131.79	12.758%	$148.6038	$148.60	$148.60	$148.60
Purchase #2	$65.56	7.848%	$70.7051	$70.71	$70.70	$70.70
Purchase #3	$114.88	3.437%	$118.8284	$118.83	$118.85	$118.80
Purchase #4	$250.81	4.386%	$261.8105	$261.81	$261.80	$261.80
Purchase #5	$134.48	7.139%	$144.0805	$144.08	$144.10	$144.10
Purchase #6	$95.51	3.245%	$98.6093	$98.61	$98.60	$98.60
Purchase #7	$223.69	6.868%	$239.053	$239.05	$239.05	$239.10
7 purchase totals =	$1,016.72		$1,081.6906	$1,081.69	$1,081.70	$1,081.70