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	$200.93	6.690%	$214.3722	$214.37	$214.35	$214.40
Purchase #2	$96.93	8.823%	$105.4821	$105.48	$105.50	$105.50
Purchase #3	$177.61	6.725%	$189.5543	$189.55	$189.55	$189.60
Purchase #4	$133.30	11.647%	$148.8255	$148.83	$148.85	$148.80
Purchase #5	$183.88	3.533%	$190.3765	$190.38	$190.40	$190.40
Purchase #6	$185.86	12.184%	$208.5052	$208.51	$208.50	$208.50
Purchase #7	$208.49	3.314%	$215.3994	$215.40	$215.40	$215.40
7 purchase totals =	$1,187.00		$1,272.5152	$1,272.52	$1,272.55	$1,272.60