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	$105.33	4.837%	$110.4248	$110.42	$110.40	$110.40
Purchase #2	$140.42	8.176%	$151.9007	$151.90	$151.90	$151.90
Purchase #3	$63.92	8.223%	$69.1761	$69.18	$69.20	$69.20
Purchase #4	$21.94	8.611%	$23.8293	$23.83	$23.85	$23.80
Purchase #5	$63.86	11.250%	$71.0443	$71.04	$71.05	$71.00
Purchase #6	$54.89	13.714%	$62.4176	$62.42	$62.40	$62.40
Purchase #7	$70.54	10.689%	$78.08	$78.08	$78.10	$78.10
7 purchase totals =	$520.90		$566.8728	$566.87	$566.90	$566.80