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	$232.40	4.796%	$243.5459	$243.55	$243.55	$243.50
Purchase #2	$219.47	10.186%	$241.8252	$241.83	$241.85	$241.80
Purchase #3	$154.42	4.691%	$161.6638	$161.66	$161.65	$161.70
Purchase #4	$172.59	4.713%	$180.7242	$180.72	$180.70	$180.70
Purchase #5	$155.65	7.626%	$167.5199	$167.52	$167.50	$167.50
Purchase #6	$89.82	13.665%	$102.0939	$102.09	$102.10	$102.10
Purchase #7	$54.60	11.865%	$61.0783	$61.08	$61.10	$61.10
7 purchase totals =	$1,078.95		$1,158.4512	$1,158.45	$1,158.45	$1,158.40