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	$44.99	13.130%	$50.8972	$50.90	$50.90	$50.90
Purchase #2	$67.69	13.592%	$76.8904	$76.89	$76.90	$76.90
Purchase #3	$57.46	4.471%	$60.029	$60.03	$60.05	$60.00
Purchase #4	$100.77	3.723%	$104.5217	$104.52	$104.50	$104.50
Purchase #5	$69.83	12.768%	$78.7459	$78.75	$78.75	$78.70
Purchase #6	$114.29	11.602%	$127.5499	$127.55	$127.55	$127.50
Purchase #7	$142.93	7.599%	$153.7913	$153.79	$153.80	$153.80
7 purchase totals =	$597.96		$652.4254	$652.43	$652.45	$652.30