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	$80.77	3.460%	$83.5646	$83.56	$83.55	$83.60
Purchase #2	$100.69	10.247%	$111.0077	$111.01	$111.00	$111.00
Purchase #3	$6.45	9.579%	$7.0678	$7.07	$7.05	$7.10
Purchase #4	$217.78	5.106%	$228.8998	$228.90	$228.90	$228.90
Purchase #5	$211.33	12.406%	$237.5476	$237.55	$237.55	$237.50
Purchase #6	$138.37	13.126%	$156.5324	$156.53	$156.55	$156.50
Purchase #7	$176.99	6.366%	$188.2572	$188.26	$188.25	$188.30
7 purchase totals =	$932.38		$1,012.8771	$1,012.88	$1,012.85	$1,012.90