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	$11.46	10.669%	$12.6827	$12.68	$12.70	$12.70
Purchase #2	$203.42	7.216%	$218.0988	$218.10	$218.10	$218.10
Purchase #3	$210.67	5.306%	$221.8482	$221.85	$221.85	$221.80
Purchase #4	$72.47	13.203%	$82.0382	$82.04	$82.05	$82.00
Purchase #5	$155.46	4.259%	$162.081	$162.08	$162.10	$162.10
Purchase #6	$143.70	9.168%	$156.8744	$156.87	$156.85	$156.90
Purchase #7	$196.86	10.120%	$216.7822	$216.78	$216.80	$216.80
7 purchase totals =	$994.04		$1,070.4055	$1,070.40	$1,070.45	$1,070.40