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	$238.85	9.195%	$260.8123	$260.81	$260.80	$260.80
Purchase #2	$212.38	13.739%	$241.5589	$241.56	$241.55	$241.60
Purchase #3	$104.36	3.626%	$108.1441	$108.14	$108.15	$108.10
Purchase #4	$48.94	11.351%	$54.4952	$54.50	$54.50	$54.50
Purchase #5	$31.56	11.466%	$35.1787	$35.18	$35.20	$35.20
Purchase #6	$232.32	11.164%	$258.2562	$258.26	$258.25	$258.30
Purchase #7	$45.45	11.874%	$50.8467	$50.85	$50.85	$50.80
7 purchase totals =	$913.86		$1,009.2921	$1,009.30	$1,009.30	$1,009.30