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	$142.68	13.593%	$162.0745	$162.07	$162.05	$162.10
Purchase #2	$75.75	10.802%	$83.9325	$83.93	$83.95	$83.90
Purchase #3	$104.66	6.266%	$111.218	$111.22	$111.20	$111.20
Purchase #4	$101.70	10.668%	$112.5494	$112.55	$112.55	$112.50
Purchase #5	$189.50	5.762%	$200.419	$200.42	$200.40	$200.40
Purchase #6	$240.35	3.113%	$247.8321	$247.83	$247.85	$247.80
Purchase #7	$241.71	12.720%	$272.4555	$272.46	$272.45	$272.50
7 purchase totals =	$1,096.35		$1,190.4810	$1,190.48	$1,190.45	$1,190.40