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	$141.26	6.448%	$150.3684	$150.37	$150.35	$150.40
Purchase #2	$224.90	12.202%	$252.3423	$252.34	$252.35	$252.30
Purchase #3	$69.63	4.647%	$72.8657	$72.87	$72.85	$72.90
Purchase #4	$13.29	8.337%	$14.398	$14.40	$14.40	$14.40
Purchase #5	$116.91	9.307%	$127.7908	$127.79	$127.80	$127.80
Purchase #6	$155.33	12.608%	$174.914	$174.91	$174.90	$174.90
Purchase #7	$78.81	5.528%	$83.1666	$83.17	$83.15	$83.20
7 purchase totals =	$800.13		$875.8458	$875.85	$875.80	$875.90