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	$11.94	3.433%	$12.3499	$12.35	$12.35	$12.30
Purchase #2	$62.27	13.333%	$70.5725	$70.57	$70.55	$70.60
Purchase #3	$194.75	9.294%	$212.8501	$212.85	$212.85	$212.90
Purchase #4	$163.90	9.473%	$179.4262	$179.43	$179.45	$179.40
Purchase #5	$66.67	8.561%	$72.3776	$72.38	$72.40	$72.40
Purchase #6	$150.46	13.836%	$171.2776	$171.28	$171.30	$171.30
Purchase #7	$197.93	10.328%	$218.3722	$218.37	$218.35	$218.40
7 purchase totals =	$847.92		$937.2261	$937.23	$937.25	$937.30