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	$80.77	3.293%	$83.4298	$83.43	$83.45	$83.40
Purchase #2	$163.32	3.616%	$169.2257	$169.23	$169.25	$169.20
Purchase #3	$39.69	10.600%	$43.8971	$43.90	$43.90	$43.90
Purchase #4	$115.26	7.205%	$123.5645	$123.56	$123.55	$123.60
Purchase #5	$172.83	3.824%	$179.439	$179.44	$179.45	$179.40
Purchase #6	$191.78	11.649%	$214.1205	$214.12	$214.10	$214.10
Purchase #7	$96.71	9.186%	$105.5938	$105.59	$105.60	$105.60
7 purchase totals =	$860.36		$919.2704	$919.27	$919.30	$919.20