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	$107.50	12.666%	$121.116	$121.12	$121.10	$121.10
Purchase #2	$74.55	11.696%	$83.2694	$83.27	$83.25	$83.30
Purchase #3	$190.97	13.477%	$216.707	$216.71	$216.70	$216.70
Purchase #4	$111.42	11.184%	$123.8812	$123.88	$123.90	$123.90
Purchase #5	$172.32	13.426%	$195.4557	$195.46	$195.45	$195.50
Purchase #6	$233.94	5.697%	$247.2676	$247.27	$247.25	$247.30
Purchase #7	$55.85	11.427%	$62.232	$62.23	$62.25	$62.20
7 purchase totals =	$946.55		$1,049.9289	$1,049.94	$1,049.90	$1,050.00