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	$62.93	5.639%	$66.4786	$66.48	$66.50	$66.50
Purchase #2	$205.89	5.245%	$216.6889	$216.69	$216.70	$216.70
Purchase #3	$198.46	13.760%	$225.7681	$225.77	$225.75	$225.80
Purchase #4	$41.94	10.274%	$46.2489	$46.25	$46.25	$46.20
Purchase #5	$79.25	9.503%	$86.7811	$86.78	$86.80	$86.80
Purchase #6	$111.29	8.527%	$120.7797	$120.78	$120.80	$120.80
Purchase #7	$178.45	7.497%	$191.8284	$191.83	$191.85	$191.80
7 purchase totals =	$878.21		$954.5737	$954.58	$954.65	$954.60