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	$52.51	13.561%	$59.6309	$59.63	$59.65	$59.60
Purchase #2	$162.28	11.668%	$181.2148	$181.21	$181.20	$181.20
Purchase #3	$94.78	6.458%	$100.9009	$100.90	$100.90	$100.90
Purchase #4	$55.54	5.110%	$58.3781	$58.38	$58.40	$58.40
Purchase #5	$113.87	6.379%	$121.1338	$121.13	$121.15	$121.10
Purchase #6	$230.89	10.604%	$255.3736	$255.37	$255.35	$255.40
Purchase #7	$33.94	10.863%	$37.6269	$37.63	$37.65	$37.60
7 purchase totals =	$743.81		$814.2590	$814.25	$814.30	$814.20