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	$243.96	5.709%	$257.8877	$257.89	$257.90	$257.90
Purchase #2	$87.45	11.594%	$97.589	$97.59	$97.60	$97.60
Purchase #3	$209.75	7.561%	$225.6092	$225.61	$225.60	$225.60
Purchase #4	$32.69	8.253%	$35.3879	$35.39	$35.40	$35.40
Purchase #5	$237.98	13.842%	$270.9212	$270.92	$270.90	$270.90
Purchase #6	$32.81	5.727%	$34.689	$34.69	$34.70	$34.70
Purchase #7	$164.32	8.781%	$178.7489	$178.75	$178.75	$178.70
7 purchase totals =	$1,008.96		$1,100.8329	$1,100.84	$1,100.85	$1,100.80