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	$139.33	3.327%	$143.9655	$143.97	$143.95	$144.00
Purchase #2	$142.87	7.617%	$153.7524	$153.75	$153.75	$153.80
Purchase #3	$105.43	13.794%	$119.973	$119.97	$119.95	$120.00
Purchase #4	$208.29	12.407%	$234.1325	$234.13	$234.15	$234.10
Purchase #5	$225.86	3.776%	$234.3885	$234.39	$234.40	$234.40
Purchase #6	$43.54	3.864%	$45.2224	$45.22	$45.20	$45.20
Purchase #7	$75.32	4.116%	$78.4202	$78.42	$78.40	$78.40
7 purchase totals =	$940.64		$1,009.8545	$1,009.85	$1,009.80	$1,009.90