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	$81.46	4.522%	$85.1436	$85.14	$85.15	$85.10
Purchase #2	$222.38	6.252%	$236.2832	$236.28	$236.30	$236.30
Purchase #3	$103.85	7.483%	$111.6211	$111.62	$111.60	$111.60
Purchase #4	$159.73	7.394%	$171.5404	$171.54	$171.55	$171.50
Purchase #5	$119.91	6.371%	$127.5495	$127.55	$127.55	$127.50
Purchase #6	$212.64	11.152%	$236.3536	$236.35	$236.35	$236.40
Purchase #7	$138.48	8.665%	$150.4793	$150.48	$150.50	$150.50
7 purchase totals =	$1,038.45		$1,118.9707	$1,118.96	$1,119.00	$1,118.90