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	$152.90	9.365%	$167.2191	$167.22	$167.20	$167.20
Purchase #2	$201.45	12.773%	$227.1812	$227.18	$227.20	$227.20
Purchase #3	$54.50	8.680%	$59.2306	$59.23	$59.25	$59.20
Purchase #4	$204.63	6.215%	$217.3478	$217.35	$217.35	$217.30
Purchase #5	$208.34	9.295%	$227.7052	$227.71	$227.70	$227.70
Purchase #6	$103.50	3.874%	$107.5096	$107.51	$107.50	$107.50
Purchase #7	$123.27	10.436%	$136.1345	$136.13	$136.15	$136.10
7 purchase totals =	$1,048.59		$1,142.3280	$1,142.33	$1,142.35	$1,142.20