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	$103.73	5.447%	$109.3802	$109.38	$109.40	$109.40
Purchase #2	$86.82	10.634%	$96.0524	$96.05	$96.05	$96.10
Purchase #3	$116.29	5.446%	$122.6232	$122.62	$122.60	$122.60
Purchase #4	$250.47	9.144%	$273.373	$273.37	$273.35	$273.40
Purchase #5	$113.38	12.462%	$127.5094	$127.51	$127.50	$127.50
Purchase #6	$178.67	10.277%	$197.0319	$197.03	$197.05	$197.00
Purchase #7	$152.73	8.696%	$166.0114	$166.01	$166.00	$166.00
7 purchase totals =	$1,002.09		$1,091.9815	$1,091.97	$1,091.95	$1,092.00