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	$144.47	12.286%	$162.2196	$162.22	$162.20	$162.20
Purchase #2	$111.59	10.724%	$123.5569	$123.56	$123.55	$123.60
Purchase #3	$141.66	7.643%	$152.4871	$152.49	$152.50	$152.50
Purchase #4	$107.70	9.769%	$118.2212	$118.22	$118.20	$118.20
Purchase #5	$105.91	3.593%	$109.7153	$109.72	$109.70	$109.70
Purchase #6	$193.41	13.327%	$219.1858	$219.19	$219.20	$219.20
Purchase #7	$30.63	4.593%	$32.0368	$32.04	$32.05	$32.00
7 purchase totals =	$835.37		$917.4227	$917.44	$917.40	$917.40