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	$245.69	6.853%	$262.5271	$262.53	$262.55	$262.50
Purchase #2	$250.88	3.382%	$259.3648	$259.36	$259.35	$259.40
Purchase #3	$20.88	12.687%	$23.529	$23.53	$23.55	$23.50
Purchase #4	$187.60	13.396%	$212.7309	$212.73	$212.75	$212.70
Purchase #5	$72.83	7.615%	$78.376	$78.38	$78.40	$78.40
Purchase #6	$92.59	3.393%	$95.7316	$95.73	$95.75	$95.70
Purchase #7	$126.56	11.422%	$141.0157	$141.02	$141.00	$141.00
7 purchase totals =	$997.03		$1,073.2751	$1,073.28	$1,073.35	$1,073.20