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	$247.40	3.292%	$255.5444	$255.54	$255.55	$255.50
Purchase #2	$11.88	6.697%	$12.6756	$12.68	$12.70	$12.70
Purchase #3	$39.34	4.277%	$41.0226	$41.02	$41.00	$41.00
Purchase #4	$200.54	6.830%	$214.2369	$214.24	$214.25	$214.20
Purchase #5	$86.54	3.650%	$89.6987	$89.70	$89.70	$89.70
Purchase #6	$139.48	13.311%	$158.0462	$158.05	$158.05	$158.00
Purchase #7	$86.82	4.584%	$90.7998	$90.80	$90.80	$90.80
7 purchase totals =	$812.00		$862.0242	$862.03	$862.05	$861.90