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	$193.78	10.396%	$213.9254	$213.93	$213.95	$213.90
Purchase #2	$139.43	9.866%	$153.1862	$153.19	$153.20	$153.20
Purchase #3	$148.98	10.261%	$164.2668	$164.27	$164.25	$164.30
Purchase #4	$90.89	12.637%	$102.3758	$102.38	$102.40	$102.40
Purchase #5	$53.68	3.390%	$55.4998	$55.50	$55.50	$55.50
Purchase #6	$76.60	11.155%	$85.1447	$85.14	$85.15	$85.10
Purchase #7	$248.89	4.253%	$259.4753	$259.48	$259.50	$259.50
7 purchase totals =	$952.25		$1,033.8740	$1,033.89	$1,033.95	$1,033.90