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	$40.40	7.849%	$43.571	$43.57	$43.55	$43.60
Purchase #2	$119.26	11.505%	$132.9809	$132.98	$133.00	$133.00
Purchase #3	$106.45	6.380%	$113.2415	$113.24	$113.25	$113.20
Purchase #4	$108.43	5.397%	$114.282	$114.28	$114.30	$114.30
Purchase #5	$119.99	13.811%	$136.5618	$136.56	$136.55	$136.60
Purchase #6	$104.61	4.810%	$109.6417	$109.64	$109.65	$109.60
Purchase #7	$15.52	4.627%	$16.2381	$16.24	$16.25	$16.20
7 purchase totals =	$614.66		$666.5170	$666.51	$666.55	$666.50