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	$238.28	13.117%	$269.5352	$269.54	$269.55	$269.50
Purchase #2	$196.72	10.273%	$216.929	$216.93	$216.95	$216.90
Purchase #3	$241.80	11.424%	$269.4232	$269.42	$269.40	$269.40
Purchase #4	$34.80	3.728%	$36.0973	$36.10	$36.10	$36.10
Purchase #5	$75.47	9.446%	$82.5989	$82.60	$82.60	$82.60
Purchase #6	$171.75	10.803%	$190.3042	$190.30	$190.30	$190.30
Purchase #7	$5.64	4.548%	$5.8965	$5.90	$5.90	$5.90
7 purchase totals =	$964.46		$1,070.7843	$1,070.79	$1,070.80	$1,070.70