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	$78.39	9.655%	$85.9586	$85.96	$85.95	$86.00
Purchase #2	$89.88	6.256%	$95.5029	$95.50	$95.50	$95.50
Purchase #3	$121.77	6.411%	$129.5767	$129.58	$129.60	$129.60
Purchase #4	$244.87	4.450%	$255.7667	$255.77	$255.75	$255.80
Purchase #5	$47.51	13.190%	$53.7766	$53.78	$53.80	$53.80
Purchase #6	$185.65	5.693%	$196.2191	$196.22	$196.20	$196.20
Purchase #7	$16.81	12.683%	$18.942	$18.94	$18.95	$18.90
7 purchase totals =	$784.88		$835.7426	$835.75	$835.75	$835.80