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	$208.30	3.374%	$215.328	$215.33	$215.35	$215.30
Purchase #2	$87.39	5.151%	$91.8915	$91.89	$91.90	$91.90
Purchase #3	$77.52	10.546%	$85.6953	$85.70	$85.70	$85.70
Purchase #4	$66.30	9.646%	$72.6953	$72.70	$72.70	$72.70
Purchase #5	$139.83	5.158%	$147.0424	$147.04	$147.05	$147.00
Purchase #6	$169.28	10.557%	$187.1509	$187.15	$187.15	$187.20
Purchase #7	$127.92	11.354%	$142.444	$142.44	$142.45	$142.40
7 purchase totals =	$876.54		$942.2474	$942.25	$942.30	$942.20