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	$9.28	10.673%	$10.2705	$10.27	$10.25	$10.30
Purchase #2	$160.62	8.353%	$174.0366	$174.04	$174.05	$174.00
Purchase #3	$226.30	10.232%	$249.455	$249.46	$249.45	$249.50
Purchase #4	$35.42	4.631%	$37.0603	$37.06	$37.05	$37.10
Purchase #5	$241.75	13.793%	$275.0946	$275.09	$275.10	$275.10
Purchase #6	$213.40	7.494%	$229.3922	$229.39	$229.40	$229.40
Purchase #7	$88.88	6.351%	$94.5248	$94.52	$94.50	$94.50
7 purchase totals =	$975.65		$1,069.8340	$1,069.83	$1,069.80	$1,069.90