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	$212.87	4.794%	$223.075	$223.08	$223.10	$223.10
Purchase #2	$160.25	5.772%	$169.4996	$169.50	$169.50	$169.50
Purchase #3	$58.83	6.312%	$62.5433	$62.54	$62.55	$62.50
Purchase #4	$63.47	8.825%	$69.0712	$69.07	$69.05	$69.10
Purchase #5	$127.82	3.664%	$132.5033	$132.50	$132.50	$132.50
Purchase #6	$240.95	6.592%	$256.8334	$256.83	$256.85	$256.80
Purchase #7	$26.41	5.772%	$27.9344	$27.93	$27.95	$27.90
7 purchase totals =	$890.60		$941.4602	$941.45	$941.50	$941.40