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	$160.82	6.761%	$171.693	$171.69	$171.70	$171.70
Purchase #2	$74.95	5.282%	$78.9089	$78.91	$78.90	$78.90
Purchase #3	$244.85	11.472%	$272.9392	$272.94	$272.95	$272.90
Purchase #4	$202.54	11.349%	$225.5263	$225.53	$225.55	$225.50
Purchase #5	$136.28	4.249%	$142.0705	$142.07	$142.05	$142.10
Purchase #6	$47.29	13.187%	$53.5261	$53.53	$53.55	$53.50
Purchase #7	$130.92	9.338%	$143.1453	$143.15	$143.15	$143.10
7 purchase totals =	$997.65		$1,087.8093	$1,087.82	$1,087.85	$1,087.70