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	$211.55	9.436%	$231.5119	$231.51	$231.50	$231.50
Purchase #2	$144.57	10.801%	$160.185	$160.19	$160.20	$160.20
Purchase #3	$50.96	6.773%	$54.4115	$54.41	$54.40	$54.40
Purchase #4	$110.97	10.573%	$122.7029	$122.70	$122.70	$122.70
Purchase #5	$180.86	8.378%	$196.0125	$196.01	$196.00	$196.00
Purchase #6	$173.45	13.221%	$196.3818	$196.38	$196.40	$196.40
Purchase #7	$109.86	13.549%	$124.7449	$124.74	$124.75	$124.70
7 purchase totals =	$982.22		$1,085.9505	$1,085.94	$1,085.95	$1,085.90