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	$55.76	10.796%	$61.7798	$61.78	$61.80	$61.80
Purchase #2	$86.70	12.571%	$97.5991	$97.60	$97.60	$97.60
Purchase #3	$56.77	5.114%	$59.6732	$59.67	$59.65	$59.70
Purchase #4	$231.56	8.579%	$251.4255	$251.43	$251.45	$251.40
Purchase #5	$204.85	7.130%	$219.4558	$219.46	$219.45	$219.50
Purchase #6	$76.51	8.612%	$83.099	$83.10	$83.10	$83.10
Purchase #7	$92.35	4.598%	$96.5963	$96.60	$96.60	$96.60
7 purchase totals =	$804.50		$869.6287	$869.64	$869.65	$869.70