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	$237.51	7.710%	$255.822	$255.82	$255.80	$255.80
Purchase #2	$238.81	9.290%	$260.9954	$261.00	$261.00	$261.00
Purchase #3	$36.45	3.276%	$37.6441	$37.64	$37.65	$37.60
Purchase #4	$28.45	5.803%	$30.101	$30.10	$30.10	$30.10
Purchase #5	$207.40	12.371%	$233.0575	$233.06	$233.05	$233.10
Purchase #6	$90.48	13.517%	$102.7102	$102.71	$102.70	$102.70
Purchase #7	$87.26	3.283%	$90.1247	$90.12	$90.10	$90.10
7 purchase totals =	$926.36		$1,010.4549	$1,010.45	$1,010.40	$1,010.40