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	$214.55	3.536%	$222.1365	$222.14	$222.15	$222.10
Purchase #2	$122.69	11.339%	$136.6018	$136.60	$136.60	$136.60
Purchase #3	$216.51	5.858%	$229.1932	$229.19	$229.20	$229.20
Purchase #4	$109.59	3.624%	$113.5615	$113.56	$113.55	$113.60
Purchase #5	$163.30	11.161%	$181.5259	$181.53	$181.55	$181.50
Purchase #6	$136.66	11.279%	$152.0739	$152.07	$152.05	$152.10
Purchase #7	$17.65	13.728%	$20.073	$20.07	$20.05	$20.10
7 purchase totals =	$980.95		$1,055.1658	$1,055.16	$1,055.15	$1,055.20