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	$217.88	9.659%	$238.925	$238.93	$238.95	$238.90
Purchase #2	$121.27	11.272%	$134.9396	$134.94	$134.95	$134.90
Purchase #3	$31.85	3.144%	$32.8514	$32.85	$32.85	$32.90
Purchase #4	$57.31	6.493%	$61.0311	$61.03	$61.05	$61.00
Purchase #5	$231.55	11.840%	$258.9655	$258.97	$258.95	$259.00
Purchase #6	$190.28	9.455%	$208.271	$208.27	$208.25	$208.30
Purchase #7	$148.47	11.587%	$165.6732	$165.67	$165.65	$165.70
7 purchase totals =	$998.61		$1,100.6568	$1,100.66	$1,100.65	$1,100.70