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	$53.55	5.326%	$56.4021	$56.40	$56.40	$56.40
Purchase #2	$69.45	5.171%	$73.0413	$73.04	$73.05	$73.00
Purchase #3	$238.57	9.203%	$260.5256	$260.53	$260.55	$260.50
Purchase #4	$135.90	6.553%	$144.8055	$144.81	$144.80	$144.80
Purchase #5	$160.44	3.111%	$165.4313	$165.43	$165.45	$165.40
Purchase #6	$57.27	6.381%	$60.9244	$60.92	$60.90	$60.90
Purchase #7	$237.40	7.429%	$255.0364	$255.04	$255.05	$255.00
7 purchase totals =	$952.58		$1,016.1666	$1,016.17	$1,016.20	$1,016.00