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	$241.72	11.541%	$269.6169	$269.62	$269.60	$269.60
Purchase #2	$17.90	10.203%	$19.7263	$19.73	$19.75	$19.70
Purchase #3	$71.92	11.815%	$80.4173	$80.42	$80.40	$80.40
Purchase #4	$113.48	12.600%	$127.7785	$127.78	$127.80	$127.80
Purchase #5	$226.54	11.863%	$253.4144	$253.41	$253.40	$253.40
Purchase #6	$105.77	12.384%	$118.8686	$118.87	$118.85	$118.90
Purchase #7	$90.85	12.872%	$102.5442	$102.54	$102.55	$102.50
7 purchase totals =	$868.18		$972.3662	$972.37	$972.35	$972.30