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	$12.45	10.829%	$13.7982	$13.80	$13.80	$13.80
Purchase #2	$162.61	13.316%	$184.2631	$184.26	$184.25	$184.30
Purchase #3	$236.39	11.793%	$264.2675	$264.27	$264.25	$264.30
Purchase #4	$103.77	9.455%	$113.5815	$113.58	$113.60	$113.60
Purchase #5	$123.75	10.382%	$136.5977	$136.60	$136.60	$136.60
Purchase #6	$79.42	3.479%	$82.183	$82.18	$82.20	$82.20
Purchase #7	$246.48	7.444%	$264.828	$264.83	$264.85	$264.80
7 purchase totals =	$964.87		$1,059.5190	$1,059.52	$1,059.55	$1,059.60