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	$143.72	8.866%	$156.4622	$156.46	$156.45	$156.50
Purchase #2	$109.33	12.630%	$123.1384	$123.14	$123.15	$123.10
Purchase #3	$191.29	6.255%	$203.2552	$203.26	$203.25	$203.30
Purchase #4	$166.45	12.778%	$187.719	$187.72	$187.70	$187.70
Purchase #5	$101.96	5.747%	$107.8196	$107.82	$107.80	$107.80
Purchase #6	$72.95	13.140%	$82.5356	$82.54	$82.55	$82.50
Purchase #7	$161.37	4.734%	$169.0093	$169.01	$169.00	$169.00
7 purchase totals =	$947.07		$1,029.9393	$1,029.95	$1,029.90	$1,029.90